macos 10.13.6. mdworker gets killed 9 by mds and lsd goes high cpu

I have a problem that involves TimeMachine, mdworker and lsd.
As soon TimeMachine kicks in to backup, lsd drives crazy (130%)
In addition the syslog shows:

695 com.apple.xpc.launchd[1]: (com.apple.mdworker.shared.03000000-0000-0000-0000-000000000000[3072]) Service exited due to signal: Killed: 9 sent by mds[67]
about two times per minute.
The problem is, that the System gets unresponsive and working with, is getting hard.