Heal tool in GIMP very slow

I’m frequently using the GIMP heal tool on photos with a resolution exceeding 3000x2000. With increasing size of the heal tool (starting approximately at >100) it gets incredibly slow and unresponsive. I’m using GIMP (recently upgraded to 2.99.16) under Ubuntu 22.04 on a Ryzen 7 5800 with a Radeon…