I repeated with an entirely new file with the same results. 42 minute play time (30 repeats of 32 BARS) and it took as long the second time to start to play as it did the first time, ~52 sec).

Have to admit I likely have never done 30 repeats for a 42 min song. So I changed to 6x. ~4 secs to play first time, then ~3 secs to play second time. I still think this is either new behavior or a bug. The second time should be and always was instantaneous otherwise I could have never played my live gigs waiting for the backing to start.

BIAB – 2025, Reaper (current), i7-12700F Processor, 32GB DDR4-3200MHz RAM, 1TB WD Black NVMe SSD, 2TB WDC Blue SSD, 1TB WD Blue, 2 TB SK NVMe, 6 TB External, Motu Audio Express 6x6