you can lower the voltage and run Prime95 v26.6, and choose the small FFTs selection - run for 15-20 minutes, if it doesn't crash, BSOD etc, then lower again in a small increment, ie 1.340 > 1.335 and if you can lower in smaller increments then do that - but when you hit the value that causes Prime95 to crash, then bump it back up 2 of those increments
but it would be best to start from scratch, as you don't know what other presets (XMP, Turbo boost, etc) that that factory OC app has selected
there's a good guide here on Tom's, would good detail, and an easy by the numbers guide over on the MSI website
https://www.msi.com/blog/intel-9th-cpu-overclocking-5ghz-with-z390-motherboards with page by page selections shown. Some of the nomenclature is slightly different from your Asus BIOS, but it won't take a second or two to recognize what they're referring to
This may or may not apply to your board, and i haven't seen anyone post about this issue, but mine was crashing while running P95 - i used WhoCrashed to pull up the mini-dump files, and it was showing a file from my virus program (Emsisoft) conflicting with a windows kernel - when i dis-abled virus program during P95 stress testing, those crashes stopped and i made it to 5.0 on my current CPU