I have reproduced a crash with auto expressions on a very small example.
You should fix this bug first and then we'll see if there are any remaining
problems with auto expressions.

To reproduce crash with Auto Expressions on a very small example:

Freeze with attached class TEST and .ecf file (has no precompile).
Click on Step into Routine.
Turn on Auto Expressions.
Click on Step into Routine 16 times.
Estudio crashes with no trace.