Intermittent fault on Korg SDD 3300

I have a Korg SDD 3300 triple digital delay rack unit that was a bit of a basket case when I got it. Someone had tried to "fix" it at some point and it had a number of issues including the wrong voltage regulator slapped in the negative rail, miswired output jacks, dead EL backlight, bad SRAM 2032...
Fixed that up and I was able to get a copy of the service manual and use the three-finger-salute button combo to get its mind back after SRAM battery replacement as is common on units of this vintage, followed the adjustment procedure in the service manual and everything seems to work as it should now except one really irritating intermittent fault remains: the LCD will occasionally garble up at power-on or in use as so:
<https://imgur.com/a/BjxoQDP>
It's annoyingly unpredictable and seems somewhat related to how it's mounted? I can power it up 25 times on the bench and it works fine making me think I solved the problem, then slide it back in the rack and it starts acting up again. I've tried a number of things like adding bypass capacitance on the display board which is separated from the CPU by good distance, disconnecting the backlight thinking it might be interference from the inverter, moving the wiring around, also recapping the PSU which I was planning on doing anyway. Doesn't seem to help.
Here is the upper digital board (the analog board is on the lower level), the lines to the LCD from the NEC Z80 variant are on the far right:
<https://imgur.com/a/DkOs2Pv>
Thinking about just trying a new display with LED backlight at this point but I've read that this unit can be finicky in accepting aftermarket LCDs.
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