Could you update to the latest version (2.1.60)? The 2.1.57 had a bug in it
This release fixes an issue in 2.1.57 that caused cards and deck presets
to be reset to the default ease, if you exported a .colpkg with compatibility
with older clients enabled, or used the downgrade and quit option, then opened
the collection again. For the former issue, this occurred to the collection you
were exporting from, and not just the .colpkg file. If you were affected by this,
running the following in the debug console after updating should restore your
cards to the ease they were at when you last reviewed them, if they were not
reviewed after the problem occurred. Please make a backup before proceeding.
2.1.58 changelogs
this issue seems likely: