Paue For & Pause Until Activity - Not functioning as expected

Hi,

Could someone help me with "Pause For" & "Pause Until" activity in nintex workfow

I used both the activity (Separately) in my workflow, I found that these activities works fine only for few workflows and later it start giving error. when I reset "SharePoint Timer service", it starts again but again for few workflows.

it gives me an error , "workflowName failed to run". when i check "View workflow History", I see that the workflow is stuck on "Pause For" or "Pause Until" Activity.

help me please.

Regards,

Yogendra Singh