Executing in an MC a program line that contains both an opcode and a comment will cause Factorio to lock-up, and to start using vast amounts of RAM (eg 12+ GB on my system). For example:

set 1 mem1 # test

Any comment after an opcode appears to exhibit this behaviour.

The following program:

" # test
" set 1 mem1 #t
" # test 2
" #test 3

Would work if I removed the #t on line 2. With the #t on line 2, it freezes as described above. So comments on their own line are fine, but not when ending a line with an opcode.

Thanks.

PS. I had to add the " before each line in the second program else this discussion page takes a # at the start of a line it as a formatting command!