I have none of these issues running thunderbird nightly, and don't remember seeing anything like this in the past, yes, I know, it's not debian's icedove and it's not in the repo's but when nightly was at "45.2.0.xx" I still seen no issues.
Mozilla/5.0 (X11; Linux x86_64; rv:51.0) Gecko/20100101 Thunderbird/51.0a1 ID:20160806030747