Odd Chain Behaviour (bug?)

I can create a short chain and have the chain include patterns from different banks no problem.

I can create a long chain and, if all the patterns are from the same bank, again no problem.

However, when I try to create a longer chain of say 20 patterns, when trying to add a pattern from a different bank things freeze in that the pattern light remains lit and I cannot do anything and hitting play deletes a pattern.

Anyone else experienced this?