Error in records site

dont try the user filters one by one.
Throw them out, then try the main filter again.
I would bet, without knowing it, that the issue is, that the conditions for the user filters are changed that moment you use the default filter.
your data is filtered and the user filters apply just to the limited result of the default filter.
-> so the user filters need to deal with the  result of the user filter as well dealing with all data properly.
I think there might be an issue. But it is a guess as long as i cannot replicate it properly on my own environment.
Sorry I have not the specific behavior of filters for 20.2 in my mind 

offtopic: I strongly recommend that the customer updates to a newer version.
Regarding support provided by appian, by the community and to get the benefits of new functionality.

can't we remove default filter?

I have to rephrase this.
in 22.1 its possible if I remember right in 20.X it wasnt possible yet. 
-> but try to fine in your record settings something like "show search box"

The error message suggests that there was an issue while retrieving data for the "Documentation Checklist" record type. It appears to be related to an unexpected error executing a query. The query includes various filters and sorting criteria.

To troubleshoot this issue, you can check the logs or error details for more specific information about the cause of the error. It may be helpful to review the query and ensure that all necessary dependencies are in place.