Horizontal stripes in display?

[danielt]

Two of my PineTime have developed this. One unsealed unit that was frequently worn without being fully water tight (double sided tape) and, at the time, I assumed water vapour ingress was settling behind the screen (which sees the biggest temperature swings so it where water vapour will tend to condense).

However I have the same horizontal lines forming on a fully sealed unit as well (which shouldn't be letting water vapour in) so perhaps my theory of what is happening is wrong!