We’ve been looking further into this issue today, and it turns out that the changes we made to allow the display of capo chord symbols (and the attendant changes to ensure that main and capo chord symbols, and chord diagrams if shown, can be aligned appropriately with each other across the width of the system) have caused a regression in the processor that finds multi-bar rest ranges.
What it all amounts to is that chord symbols should break multi-bar rests, as they did in Dorico 4 and earlier versions. This will need repairing. Sorry for the inconvenience caused in the meantime.