We have workarounds for MAGNOLIA-6821 and MGNLADVCACHE-79 in place.
As this was not suitable solution, the mentioned issues were fixed in magnolia-core-5.5, resp. advanced-cache-personalisation-1.8.1
Increase dependency to Magnolia 5.5 (and java to 1.8 to be in sync) and remove the workarounds.
MSITEMESH-13Don't create a new connection for fragment requests