Hello,
I removed my 105 cassette for the first time to clean out all the junk in it. I installed it back and when I rode my bike this morning I had trouble shifting in the middle gears and my chain even got stuck while I was going downhill. I installed it with all the spacers and the numbers facing outwards. Did I do something wrong? Is it just a matter of adding more lube? See cassette picture below.

Picture of cassette (yes it got dirty again from today's ride):