This in not necessarily the case. This is just where the memory happened to be out.
Java will spend more and more time garbage collecting when it runs out of memory which explains the high load on the system.
I had the same problems, even with OH 2.5 and this was the reason I migrated to Groovy rules and started to develop a metric addon.
Using metrics I could see that the memory would build up over a couple of days.
With RPi 4 (at least the 4GB+ versions) the problem isn’t that present any more, but with smaller memory I had this a lot.
Different reasons can lead to the same symptoms here so we should not mingle everything. I think removing all DSL rules and see if this still occurs is the first important step.