@User Here's the output. I could tarball the relevant files, if it would help. netgen version is

Netgen 1.5.192

from

commit a984ac1

(gdb) up
#1 0x00007fffede1ce41 in Tcl_Strdup (s=0x1 <Address 0x1 out of bounds>) at tclnetgen.c:4309
4309	  slen = 1 + strlen(s);
(gdb) up
#2 0x00007fffeddf678c in CopyProperties (obj_to=0x173b0040, obj_from=0xc196050) at netgen.c:2503
2503	     obj_to->model.class = strsave(obj_from->model.class);
(gdb) print *obj_from
$1 = {name = 0xc097b20 "properties", type = -4, model = {class = 0x1 <Address 0x1 out of bounds>, port = 1}, 
 instance = {name = 0xf6fc110 "\340z\t\f", props = 0xf6fc110}, flags = 0 '\000', node = -2, next = 0xc195e50}

Yes, please tarball the relevant files---I only need the two netlists being compared. The "properties" record is not supposed to be able to have a model.class value that isn't either a null or a string. I have no idea how it got that way, but I need to track it down to where it happened.

@Tim Edwards Sorry, I'm running on google cloud and can't figure out how to get the data out yet, so it may take a while. I set up a bucket, but have to do something else, I guess.

Thanks, I'll try to get around to looking at it today.