Fixed rate in expression tags

I have an expression tag that needs to be recalculated once per second. The expression is very simple (adds the value of another memory tag).

I am using a fixed rate 1000ms. But recalculation occurs every 15-20 seconds.

Why might this be happening? What else affects the recalculation period?

Memory and CPU are used by 20%

Thanks in advance/

Possibly other tags in the scan class/tag group are stalling the rest. (What version of Ignition?) Tags use a thread pool to manage multiple tasks, so it is possible to stall, especially with tag events that execute long-running code.

Consider making a tag group just for this item. Also consider using a gateway timer script to do this instead of an expression.

Same problem
Expression tag value execution with big delay consider less tag group period

Please advise