[Bug] Steam causes portal 2 source mods to lag and crash

[Blue]

I am currently developing a source mod for Portal 2- I have noticed several very strong lag-spikes that are often followed by crashes which also affect steam (steam crashes; not just portal 2, and they always both crash simultaneously.)

using the +showbudget command in-game, I was able to confirm that indeed the lag spikes are caused by steam. Often, there are also errors in the developer console stating that there was a problem getting a file from the UGC server.

I have asked other source mod developers and they are having the same issues. In addition, my playtesting team has been affected by this as well.

My computer specs:
https://imgur.com/kF0kcrg

[D4rKNFS]

I have the same problem as well