Synchronisation problems with Elements Core

Using Elements Core Version elements-0.18.1.11 (64-Bit) on Linux Mint.

It correctly synchronized everything full after installation - but now when I am starting elements-qt, it boots up correctly but never synchronizes itself for the newest blocks after initial synchronization. Network connections are most of the time between 1 and 9, sometimes a short time 0 - but it never synchronizes the rest. Had this failure also on another computer with a different internet cionnection. Bitcoin core itself does fine with synchronizing.