This is a common problem with foam backed headliners in the South. Keep a hands off approach ressisting the urge to touch the headliner and take measures to control the heat/humidity levels in the coach to help control the speed of deterioration. They tried a one piece fabric design which works better unless one of the dividers between the four foot ceiling backer panels comes loose and then you have to slit the fabric to get to them and then put external divider strips in their place. To me the long term solution is to pull it all down and replace with an unbacked wall carpet putting new divider strips between the sections.
2001 Winnebago Adventurer WFG35U