This read-only counter tracks the number of expired reassembly timers, meaning cases where the switch started reassembling an AAL5 frame from incoming cells but didn't receive the remaining cells to complete it before a timeout, forcing the partial frame to be discarded. This is a direct symptom of cell loss severe enough to strand a frame mid-assembly, distinct from CRC or length errors which occur on frames that were at least fully received. An admin seeing cktATMAAL5ReassemblyTimerError increasing alongside rising general cell-discard counters would conclude that cell loss is severe enough to be breaking frames outright rather than just causing minor corruption.