Converted Lemmings Plus I from the NXP via NXPConvertor.
Medi 1 and Psycho 13's replays fail, due to removal of steel area support. I fixed this up in Medi 1's file via NLEditor (for Psycho 13, I copied / pasted via a text editor, so this was unaffected). The talisman data became corrupted in the process.
Corrupted data (after saving from NLEditor)
$TALISMAN
TITLE Complete Medi 1 with max 4 builders and 2 each of other skills.
ID 16
COLOR Gold
CLIMBER_LIMIT Gold
FLOATER_LIMIT Gold
BOMBER_LIMIT Gold
BLOCKER_LIMIT Gold
BUILDER_LIMIT Gold
BASHER_LIMIT Gold
MINER_LIMIT Gold
DIGGER_LIMIT Gold
$END
Correct data (directly after NXPConvertor conversion)
$TALISMAN
TITLE Complete Medi 1 with max 4 builders and 2 each of other skills.
ID 16
COLOR gold
CLIMBER_LIMIT 2
FLOATER_LIMIT 2
BOMBER_LIMIT 2
BLOCKER_LIMIT 2
BUILDER_LIMIT 4
BASHER_LIMIT 2
MINER_LIMIT 2
DIGGER_LIMIT 2
$END
EDIT: This also happened on a LPIII level, where it corrupted a talisman save requirement rather than a skill count.
I already found this bug two days ago and fixed it. This will be released with the next update.
Semi-related bug: If any level in the "levels" folder (or otherwise included in NeoLemmix's level selection list) has such talisman data, NeoLemmix may refuse to start, or if it does start (in my experience, it would start successfully under these conditions as long as no save data existed), it may give error messages (sometimes fatal, sometimes not) when trying to open the level select menu.
Thanks. I now fixed this, too. The game no longer crashes but displays an error message instead.