Question

Why do I get those warnings? How to stop them from appearing? Does this do any harm to OCR and performance?

Answer

There are several different Event Data under the "Event ID 1 from source FlexiCapture User Station cannot be found" warning.

1)  FlexiBr1
  Could not process the task
In that case, you should check the Background Tasks window as it may contain the log of the task that couldn't be processed as on the screenshot below:


2) ​FlexiBr
MSG_EN_BP_STTM_DELETE_TASK_NOT_UPLOADED_TO_SERVER $str8989[ id = {"specific ID} , tenantId = 0 , GetEnterpriseTaskId() = 0 , state = STS_Succeeded ]
​
The second one is a bug. The fix of this issue was implemented in build 12.0.4.678.

It was tested by our development team. We haven't noticed a performance decrease caused by those warnings.

So, please, try to download and update your FC build to the latest release over the link below:
ABBYY FlexiCapture 12 Release 4