I turned these adapters (thank you Amazon) and put my old CPL "free" that they did not ask anything of stability problem;
given the many positive reviews, I do not think the CPL 500 TP-LINK are bad, but they are apparently allergic to my electrical installation
Later, I bought (more expensive) devolo 650+, which allowed me to have a better throughput, which are much more stable (some small incidents anyway)