I never had this problem maybe because I only had the 5 original instruments when adding, deleting, copy and pasting, etc, measures in my unfolded songs. The OP stated "I've built a track and entered chords , added soloists, keyboard and other instruments and now I find I want to insert 4 bars into the middle which essentially are intended to copy the previous 4 bars." Note I am assuming the OP used the utility tracks go add those other instruments.

My question to those more familiar with BiaB would adding soloist and utility tracks be the problem?

Whenever I get something stuck in the back of my throat, I dislodge it by drinking a beer.
It's called the Heineken Maneuver.

64 bit Win 10 Pro, the latest BiaB/RB, Roland Octa-Capture audio interface, a ton of software/hardware