I had similar problem with display - the numbers simply dissapeared or became +-2888 or something like that.... I had carefully opened the display "block" and then closed and tighten it all back together and it just started to work as it should work, so I think it is very sensitive to misalignment of contacts due to temperature changes & so on.
I think this is most likely the problem.
I do use a digital device in my photographic pursuits when necessary.
When someone rags on me for using film, I use a middle digit, upraised.