Plugin error after updating the code

Hey!

Fairley new to the assembly/plugin part, so I have a working assembly code on (on-premise) v9.0 that we needed to update a single line in it (just a regex to check a string field against), and once I update it, it starts producing various errors, any idea what the issue might be?

the old regex:

Regex repeatedRegex = new Regex(@"(\d)\1+$");
if (repeatedRegex.IsMatch(contactMobileNumber.Substring(2)))
{
    throw new InvalidMessageException("Invalid repeated mobile number");
}

the updated regex:

Regex repeatedRegex = new Regex(@"(\d)\1{6,7}");
if (repeatedRegex.IsMatch(contactMobileNumber.Substring(2)))
{
    throw new InvalidMessageException("Invalid repeated mobile number");
}

the errors I started getting are the following:

Url = , Exception = System.ServiceModel.FaultException`1[Microsoft.Xrm.Sdk.OrganizationServiceFault]: Exception output::
System.Data.SqlClient.SqlException (0x80131904): New transaction is not allowed because there are other threads running in the session. at
System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction) at
System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)  
at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)     
at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)     
at System.Data.SqlClient.TdsParser.TdsExecuteTransactionManagerRequest(Byte[] buffer, TransactionManagerRequestType request, String transactionName, TransactionManagerIsolationLevel iso... (Fault Detail is equal to Exception details:   
ErrorCode: 0x80040216  Message: Exception output:: System.Data.SqlClient.SqlException (0x80131904): New transaction is not allowed because there are other threads running in the session.     
at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)     
at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)    
at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)     
at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)     
at System.Data.SqlClient.TdsParser.TdsExecuteTransactionManagerRequest(Byte[] buffer, TransactionManagerRequestType request, String ...).

Url = , Exception = System.ServiceModel.FaultException`1[Microsoft.Xrm.Sdk.OrganizationServiceFault]: System.InvalidOperationException: The connection was not closed. The connection's current state is open.    
 at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)    
 at System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry)    
 at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)    
 at System.Data.SqlClient.SqlConnection.Open()    
 at Microsoft.Crm.CrmDbConnection.InternalOpenWithRetry(IDbConnection connection, String descriptionText)    
 at Microsoft.Crm.CrmDbConnection.GetCreateAndOpenConnection()    
 at Microsoft.Crm.CrmDbConnection.Open()    
 at Microsoft.Crm.SqlExecutionContext.InitConnectionAndTransaction()    
 at Microsoft.Crm.SqlExecutionContext.EnsureBeginRequest()    
 at Microsoft.Crm.SqlExecutionContext.get_Connection()    
 at Microsoft.Crm.BusinessEntities.ExecutionContext.OnErrorRequest()    
 at Micros... (Fault Detail is equal to Exception details:   ErrorCode: 0x80040216  Message: System.InvalidOperationException: The connection was not closed. The connection's current state is open.    
 at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)    
 at System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry)    
 at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)    
 at System.Data.SqlClient.SqlConnection.Open()    
 at Microsoft.Crm.CrmDbConnection.InternalOpenWithRetry(IDbConnection connection, String descriptionText)    
 at Microsoft.Crm.CrmDbConnection.GetCreateAndOpenConnection()    
 at Microsoft.Crm.CrmDbConnection.Open()    
 at Microsoft.Crm.SqlExecutionContext.InitConnectionAndTransaction()    
 at Microsoft.Crm.SqlExecutionContext.EnsureBeginRequest()    
 at Microsoft.Crm.SqlExecutionContext.get_Connection()    
 at Microsoft.Crm.BusinessEnt...).

Url = , Exception = System.ServiceModel.FaultException`1[Microsoft.Xrm.Sdk.OrganizationServiceFault]: SqlTrans - Encountered disposed Transaction when it should not be disposed (Fault Detail is equal to 
Exception details:   ErrorCode: 0x80040218  Message: SqlTrans - Encountered disposed Transaction when it should not be disposed  TimeStamp: 2023-06-13T09:11:36.9232978Z  --  
Exception details:   ErrorCode: 0x80040218  Message: SqlTrans - Encountered disposed Transaction when it should not be disposed  TimeStamp: 2023-06-13T09:11:36.9232978Z  --  
Exception details:   ErrorCode: 0x80040216  Message: System.ObjectDisposedException: Cannot access a disposed object.  Object name: 'CrmTransaction'.: Microsoft Dynamics CRM has experienced an error. 
Reference number for administrators or support: #8756C8B3  TimeStamp: 2023-06-13T09:11:36.9232978Z  --  ).