Hi dimitrismvrm,
This type of error in the ECLR generally appears when there is a memory leak in managed code, e.g. in a custom C# library.
You can try to isolate the code that is causing this error, e.g. by removing custom library(s) and checking if the problem still happens. Once you have isolated the problem code, you should check it for memory leaks and other issues.
BR,
vcosic