I can't speak on the 2018 models, but I do know this has been a problem since 2014 with many tvs (and not just vizio). Vizio actually went as far as to claim the issue is actually the PS4 and way it sends data over HDMI in a sometimes convoluted and fragmented way. Like it'll fall behind then catch up with a surge of data packets and on the receiving TVs end it looks like a desync, so the tv requests a new handshake. This is what causes the blackout. Something like that. Sony never actually fixed that issue and I believe when they patched it in 2015-2016 tvs vizio just told the firmware to NOT request resync when PS4 pro messes up the packets, so you'll just drop an unnoticeable frame or two instead of losing screen while it's doing a new handshake. Sadly, they left all 2014 p series 4k tvs in the dust and they never got the fix, any owner of that year basically has had to deal with random dropped pictures for the last few years with no fix in sight.
Although I don't think even that explanation ever explained why sometimes initial sync also fails, where you have to trigger a new handshake to fix it by either power cycling tv, changing input off then back on the PS4, or unplugging or replugging the HDMI cable (basically anything to cause a new handshake). Maybe that's a glitch with their fix that tells it not to handshake on crap packets, causing it to not handshake at all on initial sync if the PS4 sent malformed garbage right off the bat. 🤔
It also wouldn't explain why it's losing sync randomly as well for you on 2018 tv, which you would assume incorporates any fixes they have from earlier generations. I have no doubt their 2018 tvs should have their "fix" for handling PS4 Pro. I assume you've already verified all fundamentals, tried different HDMI cables rated for 2.0 speeds, etc?
I finally replaced my 2014 vizio with 2018 900F from sony this year, and surprise surprise a sony tv knows how to handle sony's BS from the PS4 pro. Easy to make your own tv work around your own console bugs
But I will say that the sony doesn't do local dimming as well as vizio, i don't think anyone does it as well as vizio. It's only thing that's regrettable to me. However, having a TV that I know works great with PS4 pro (main use of tv) with all the bells and whistles (full bandwidth 4k + HDR with no sync issues) was critical to me. I feel your pain, I literally dealt with it for 4 years. Hopefully one of the actual 2018 owners can tell you there is a work around though. I was just sharing the technical background of issue since I spent a lot of time dealing with it.