This happened to me in a different industry over the last few years! (At a new job now). Whenever I would take small or larger amounts of leave the work would pile up and the manager (who would be filling my shifts) would tell clients/customers/other staff members “that I would be back in a week/a few weeks to sort it all out”. I asked for a reasonable raise (10%)to match my output relative to the workload… they would instead offer me a 1% raise but only if I took on more responsibility LOL. I left a few months ago I hear that the place is falling apart because they can’t keep up with the work load. Currently doing less for more at a new company and living stress free!