Something went wrong a couple of updates ago

Following a Thunderbird update (I think it was 2 updates ago) it changed the behaviour of the description field in the new events window. I use thunderbird in a dark screen mode, and everything works perfectly, except when I try to type something into that description window. I'm now tying black (intead of white) on an almost black background. It's virtually impossible to see anything I'm trying to type. All the other fields are typing fine, white on black. If I open an entry on my calander now, it's fine, apart from that description field, which is also displaying text as black on black. It's also the same if I reopen the entry for editing. I had hoped the next update was going to correct this anomally, but it didn't. Is anyone aware of / reported this issue? Will it be fixed in the next update? Thank you for looking at this. Oh, nearly forgot, when I highlight the black on black text by clicking and dragging (prep for cut / copy & paste) the black text actually shows up as white text on a blue background whilst the field is 'live' moving onto something else, the text remains withe on a grey background. Hope this helps.