I'm working with Lazarus 1.6 under Xubuntu 16.04 LTS, and both Lazarus itself and its apps work fine there.
The problems is that my Lazarus applications fail when running under Debian 9.1.
I tested with LXDE, XFCE and KDE, in two different computers, all have the same problem, when the user types anything, either in a TEdit or TMemo, each key press generates two letters.
If the user types abc, the result is aabbcc.
TSynmemo works perfectly.
I tested two of my own apps, and also compiled a minimal app (just a form with a memo) and it fails too.
Of course, non-Lazarus apps run fine under Debian 9.
It is a Lazarus bug or what?