PSIP, or lack thereof, can be a major problem. Remember when both KAXT and KRCB were using virtual channel 22, their old analog channels? Some tuners would show two sets of 22's, while others would show the first one that they got when scanning, or a mix of both. KAXT would lose in most cases, because the scan would get a 22 from KRCB on 23, so when it got to channel 42, it would skip it. Some tuners, like my Sony TV, would give me 22-1, 22-2 and 22-3 from KRCB, then 22-4 through 22-20 from KAXT. KAXT 22-1, 22-2 and 22-3 weren't available.
KAXT solved the problem by going to the FCC and requesting to use channel 1 as their virtual channel. The FCC said OK, so they became the first TV channel 1 on the air. New York City cable had a news channel on 1, but it was cable only.
What can be confusing with PSIP vs no PSIP is that several stations are transmitting on channels that are the virtual channels of another station. Examples: KTNC 14 vs KDTV 14, KAXT 42 vs KTNC 42, KEMO 32 vs KMTP 32, KRON 38 vs KCNS 38, KTVU 44 vs KBCW 44, KQEH 50 vs KEMO 50. Lack of PSIP on any of these stations can cause problems for the other.
I remember when I was still working at KGO and they used to have a PSIP problem. That's when they were transmitting on channel 24. Their PSIP generator would quit working occasionally, so instead of showing up as channel 7 they could only be received by tuning to channel 24. They had to replace the PSIP generator.
KTLN used to have problems with their PSIP generator all the time. You'd often find them only on channel 47 with nothing showing up as channel 68. They finally got that fixed and haven't had a problem for a long time.
I still think that PSIP was a terrible idea in the first place. Yeah, stations wanted to keep their old analog channel ID, like KTVU, there's only one 2, KRON 4, ABC 7, etc., but I think that viewers would have quickly learned their new channel numbers and we could have avoided the PSIP problem entirely.