Created attachment 150611 [details]
example

SUMMARY
The filter layer "halftone - pattern" is not properly applied when a document is opened

STEPS TO REPRODUCE
1/ Create a document with a filter layer artistic>halftone
2/ Choose any pattern except the first one 
3/ Save document 
4/ Close document 
5/ Open document 

OBSERVED RESULT
1/ applied pattern is not the expected one 
2/ Open filter layer properties: we can see selected pattern is the expected one
- pattern reference is properly saved in document
- pattern reference is properly selected when opening the filter layer properties

Problem is really when document is opened, the wrong pattern is used

   
EXPECTED RESULT
==> When document is opened, the expected pattern should be applied

ADDITIONAL INFORMATION
From memory I already saw it when started to use Krita 5 (problem as not here with Krita 4)