Graphical Issues pursuant to an engine upgrade

Hello! I recently upgraded my company's project from Unity 5.6 up to Unity 2019.4.22f1 and have been having some issues with graphics since then. Either this is because newer versions rely on a render pipeline, which we originally did not have, because we were using custom shaders, or some combination of the two. Either way the graphics of the game are broken in a way that neither I nor the other coder understand. We have checked the shaders and the lightmaps, but neither seem to be the culprit, at least not individually. We adjusted both separately, then together, then in combination, and while some thing would work better in editor, they never worked in build versions. Another issue is that occasionally the terrain will just turn white. This has been plaguing us for a while, and I'm hoping that someone may be able to help!

 

I am presently shipping all my Unity 5.6.6f2 projects on Unity 2018.4.19 and they work perfectly, building for iOS and Android. Are you able to consider Unity 2018 LTS instead?

 

Unity 2019 is the version that we're building for because we have a few new features that require plugins for it. But, fortunately, 2019.4.22f1 is the LTS for 2019.

 

The anomaly is reported here also:
https://forum.unity.com/threads/err...bal-property-sheet.510126/page-2#post-8007968

 

I haven't seen any errors in my log though, it thinks that it's working just fine for some reason.