Around 160 activities in my feed, i.e. as usually… iOS mobile app, just in case it matters. 

Any chance there were some connectivity issues on your end? The feed doesn't load at once, rather part by part as you keep scrolling, so if your feed appears shorter, it might be because Strava couldn't load the next part. (Just guessing though.)

I have the exact same issue. Have tried on my mobile network, and 2 different WiFi connections and nothing. I also only see a couple of activities.