How can FINDSET fail after NOT ISEMPTY

I've been seeing a very weird issue in our BC14 CU19 code where the following fails:

[...]
IF NOT ItemAnalysisView2.ISEMPTY THEN BEGIN
  ItemAnalysisView2.LOCKTABLE;
  ItemAnalysisView2.FINDSET(TRUE, TRUE); 
  [...]
END;

ItemAnalysisView2.FINDSET(TRUE, TRUE); fails with the error that no record has been found within the filter.
How is this possible immediately after ISEMPTY returned FALSE, which means there should be a record in the table? The filter doesn't change between both lines.
Could it have something to do with the .LOCKTABLE line when FINDSET(TRUE) is also implicitly calling LOCKTABLE on that record?

The full code is a modified version of the UpdateAll() function in Codeunit 7150:

ItemAnalysisView2.SETRANGE(Blocked, FALSE);
IF DirectlyFromPosting THEN
  ItemAnalysisView2.SETRANGE("Update on Posting", TRUE);

IF ItemAnalysisView2.ISEMPTY THEN
  EXIT;

InitLastEntryNo;

IF DirectlyFromPosting THEN BEGIN
  ItemAnalysisView2.SETFILTER("Last Entry No.", '<%1', LastValueEntryNo);
  IF ItemAnalysisView2.ISEMPTY THEN BEGIN
    ItemAnalysisView2.SETRANGE("Last Entry No.");
    ItemAnalysisView2.SETFILTER("Last Service Entry No.", '<%1', LastServLedgEntryNoG);
  END;
END;

IF NOT ItemAnalysisView2.ISEMPTY THEN BEGIN
  ItemAnalysisView2.LOCKTABLE;
  ItemAnalysisView2.FINDSET(TRUE, TRUE);
  REPEAT
    UpdateOne(ItemAnalysisView2, Which, ItemAnalysisView2."Last Entry No." < LastValueEntryNo - 1000);
  UNTIL ItemAnalysisView2.NEXT = 0;
END;