See the attached example pk3, just load up map01 and walk straight ahead. I'm using a custom LineTracer class and telling it to skip (return TRACE_Skip) when it hits a two-sided wall, and TRACE_Stop for pretty much anything else. This works fine for the vast majority of cases, but a situation I ran into in VESPERAS.WAD from the Master Levels (which the pk3's MAP01 is a massively stripped down version of) has this particular thin (4 units) sector that seems to cause a crash. I've played lots of other pwads with equally fine detailing without a problem.
Example code (same as in the PK3) follows. The gzdoom-crash.log file is included in the PK3 as well.
If it avoids the crash it should be ok. If it is 100% correct I cannot really say. I've seen too many surprises with the Doom engine over the years where seemingly reasonable changes created the weirdest bugs.
Let's just merge it and see what happens.