Not like me to be done on Friday, still less posting first (if indeed I have). I found this very straightforward, but rather tedious, with lots of the same operation, occasionally speeded up with a spreadsheet. I thought the hidden feature would prove challenging, but it didn't.
I usually enjoy numericals, but this was a chore. The common feature was immediately obvious and the route around the grid felt almost forced ... so no lateral thinking or inspiration required.
This was incredibly tough - the decision whether to wilt under the sheer slog or persevere to continue my run of entries (not all correct, i hasten to add). Very clever construction, but nothing of the logical sequence that makes a good numerical.