K12MIT on PDP-12

So, with the help of you here, I was able to create OS/8 LINCtapes and to run SerialDisk. Everything runs very fine. Now comes the next thing: I want to have K12MIT, and it is no problem to compile or load the program. *But*: When I start K12MIT I don't get the prompt. I see the welcome message, and it correctly identifies the machine as a PDP-12, but that's it. As I've found out it apparently overwrites its code, the processor is looping around address 3600-3620. Examining the memory reveals that the code at 3600 has been overwritten with junk. So it's clear that it won't run anymore. What happens? Was anyone else able to run K12MIT on a PDP-12? BTW the same binary runs fine on a PDP-8, be it a real machine or SIMH. Christian