No I have not experienced the problem again.

Me and my friends built a base, dropped items on multiple occasions (several days in-between as well) server restarts 4 times a day, nothing have disappeared.

Can confirm this bug. However in my experience all players within like 200m gets the error. My friend who was like around 300m away from the car did not get client crash, but the friend who was standing next to the car got it.
The infected which is on the roof at the moment, will slowly start "hovering" upwards in the air just before the crash. When the player who was driving the car at the moment logs back into the server, he will be catapulted into the air, fall down but survive (survived all 3 times this happen). A workaround for this at the moment is to get one player, which was not in the car at the moment, to move the car before the driver/passenger logs back in.

This does also happen on stable.
The server was empty at the time (just me playing) when the bug happened.
It happens for all guns. (Do not know if the same happens to pistols)
If you try to interact with an weapon when riding a car you also get this bug.

After server has restarted you can glitch trough walls, you are unable to walk up watchtowers as you glitch trough the stairs.

Same thing happend to a friend of mine but he died as he entered an Sedan.
When he had exited the server and logged back in he spawned with all his gear outside the vheicle.

Maybe it's due to the Stable update and that the servers is currently not connected against the hive?

You need to change gear which you can do on Q and E while driving the bus.

Almost forgot, when I was in the driverseat and asked my friend to kill me (as I was stuck) he was unable to knock me out or kill me with his pickaxe.
When I had relogged all my clothes and items was completely ruined but my character was fine.