iPod Touch 2nd gen will not longer sync with newer iTunes
I did some testing on my iPod Touch 2nd generation (model A1288).
It was working no problem previously on earlier versions of iTunes.
With iTunes 12.8 (12.8.0.150) on OS X 10.13.6, iTunes gives error "invalid response received".
With iTunes 12.9 (12.9.0.164) on OS X 10.14, iTunes gives error "invalid response received".
With iTunes 12.6 (12.6.2 from https://support.apple.com/downloads/itunes) it works fine, it shows up in iTunes and can be used normally.
It looks like Apple has broken sync with the iPod Touch 2nd generation in the recent versions of iTunes (I wasn't able to test iTunes 12.7)
Apple: this needs to be fixed. Please test sync with an iPod Touch 2nd generation and iTunes 12.9 and fix the problem.