This isn't actually a bug, it's intentional. It looks better to have the lem explode a bit further into the blasticine graphic; the trigger point from when this was previously water was way too high, so it looked like the lems barely touched it.
Maybe there's a happy medium somewhere? We can always bump the trigger area up a couple of pixels.
Regarding any SLX features affecting existing content, a quote from
this topic:
it's been said from the beginning that the SLX development isn't concerned with previous (Neo)Lemmix content; this isn't to be dismissive or inconsiderate of the work that has gone into the many fantastic NL packs over the years, it's so we can have something of a fresh start and generate new ideas free from having to worry about existing content preservation.
Whilst it is
possible to play any made-for-NeoLemmix pack in SuperLemmix, most will require at least some tinkering here and there to make them compatible. If you plan on doing so,
please ask the author's permission before porting any pack to SuperLemmix - just a reminder.
I realise that simply playing a pack doesn't constitute making a port, but by doing so you're bound to encounter problems sooner or later. With the author's permission in any such case, I'm sure we can make the packs SuperLemmix-ready.