Works, but display fades

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    I inherited a partially-done OSSC 1.5 kit that had most of the passives and a couple ICs soldered. Buddy couldn’t find a few parts, got impatient and bought a built one. Some of the joints looked a bit dodgy, so I reflowed as needed, got the missing parts and finished it. It works; LED solid green, reacts to IR, shows test pattern, doubles lines with my SNES etc. The problem is within a minute or two, the LCD’s contrast will fade, then go out (the backlight stays lit). After power-cycling, it sometimes stay blank, sometimes it will show characters again but the contrast fades much sooner (<20 sec), then after one or two more times on/off, it’ll just stay blank. The longer I leave it off, the longer it’ll have proper contrast, unfortunately never long enough for me to program the remote.

    This behaviour suggests to me (with my very limited knowledge) that a capacitor is involved. I can solder well but my theory and troubleshooting skills are underdeveloped.

    I have found no shorts so far poking around between the display and the FPGA. He went with a blue transmissive STN LCD (NHD-C0216CZ-NSW-BBW-3V3datasheet) instead of the BOM’s transflective FSTN (NHD-C0216CZ-FSW-FBW-3V3datasheet) But looking at the datasheets, they both use the ST7032 controller and all specs seem the same.
    The LCD was stored loose in a drawer for a while though; could it have been ESD damaged? The board and the rest of the components he had were stored in metallic bags and black conductive cardboard boxes.

    Any idea what might be the problem or what troubleshooting steps to take next?

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