I've never seen a power-strip/splitter usage function well. Your experience only reflects the usual manufacturer recommendation: "don't use a power strip".
I recently installed six sets of the TP-Link TL-PA6010 AV2s in six 200 & 500 working situations, and three of those TP-Links failed to connect. I plugged back in the old units and they continued to work fine.
I did a few more tests (ensuring the units themselves worked, yes they do) but I didn't investigate each location's wiring because, well, the joy of the Powerlines is that they work or don't. Quick, easy. I've written the Fails off as a pickier handling of line noise, or interference, or ?? something else. Those 3 failed sets work for other customers, though, and I left it at that.