Vijeo citect V7.0 R3 / OFS V3.31 Patch A

To be fair, this is a very old configuration, and you should upgrade as soon as you can.
I even had to look up if Citect 7.0 supports MultiProcess mode, and it does. This may have to do with your problem, I think.

Does Citect run in multiprocess mode in your setup? If it does then the Runtime Manager shows seperate entries for Client, Alarm Server, Trend Server, I/O Server and Report Server. It can be enabled/disabled in the Computer Setup Wizard.

If your setup does not run in multiprocess mode, then any function in your Citect system can temporarily suspend I/O processing or handling alarms, etc. Examples of blocking functions are: cicode FOR or WHILE loops with no SleepMs statements in them, reading to/writing from files; executing external programs; calling DLL-functions or executing badly designed cicode or VBA functions.

In Multiprocess mode, only the process that executes one of these blocking function will be suspended, but not the other processes.
Howerver, switching Multiprocess mode on for a project was not engineered for this mode may lead to unexpected behaviour: Local Variables and GLOBAL or MODULE cicode variables are local to the Citect process instead of the whole computer and some system functions only work in a server process (like some I/O Device functions) or a client process (like animation and display functions).

So fixing your problems and/or upgrading to a newer version will involve some (re-)engineering.

Best regards,
Patrick

To be fair, this is a very old configuration, and you should upgrade as soon as you can.
I even had to look up if Citect 7.0 supports MultiProcess mode, and it does. This may have to do with your problem, I think.

Does Citect run in multiprocess mode in your setup? If it does then the Runtime Manager shows seperate entries for Client, Alarm Server, Trend Server, I/O Server and Report Server. It can be enabled/disabled in the Computer Setup Wizard.

If your setup does not run in multiprocess mode, then any function in your Citect system can temporarily suspend I/O processing or handling alarms, etc. Examples of blocking functions are: cicode FOR or WHILE loops with no SleepMs statements in them, reading to/writing from files; executing external programs; calling DLL-functions or executing badly designed cicode or VBA functions.

In Multiprocess mode, only the process that executes one of these blocking function will be suspended, but not the other processes.
Howerver, switching Multiprocess mode on for a project was not engineered for this mode may lead to unexpected behaviour: Local Variables and GLOBAL or MODULE cicode variables are local to the Citect process instead of the whole computer and some system functions only work in a server process (like some I/O Device functions) or a client process (like animation and display functions).

So fixing your problems and/or upgrading to a newer version will involve some (re-)engineering.

Best regards,
Patrick