Im not sure meltdowns are anything particularly new for TOM, right back to the BY days. I seem to remember a TV documentary featuring Britannia and most of the storylines involved delays. I have had the minsfortune to have 2 14 hour delays with TUI (still Thomsonfly back then) on one holiday. Haven't booked a summer package holiday since.
Maybe there is less slack in the system across aircraft/crew and ground staff this year making the problems more widespread across the system.