I'm wondering if Gmod's November Update has increased the game's resource usage somehow.
I have an older laptop and was doing fairly well on all TRP maps for several years until a month or so ago, then I had the exact same issue that Skyrim had (first noticed on Salvation, but apparently fixed after a soft server restart).
I also have a very hard time connecting when the server is on a poorly optimized, large filesize map- e.g. the Stalker maps, Boreas, Vyten, even had this issue with GM_Marsh. I always timed out on these maps without fail the past month, missing most/all events in the process. On top of that, Gmod periodically CTD's at random times, but especially when attempting to connect to said maps. When I do connect, I usually have the empty inventory glitch and several lua errors.
I'm convinced either my computer is now getting too old to play GMod effectively, or Gmod has somehow updated something that is causing certain people issues arbitrarily.