This one is somewhat inconsistent but seems to be repeatable. Also seems related to the fixture sheet update bug since you can select fixtures not in the sheet and they show up. or recall the fixture sheet.
Patch 10 Dimmers
Store all 10 fixtures in World 2
Select world 2 and fixture 1 is missing
Now Add 10 RGB Pars to the patch
Select World 1 then world 2 and Fixtures a and 2 are missing from the fixture sheet.
Select world 1, Select all fixtures and store into World 3