Stacking while creating previews, get internal error

If I am creating 1:1 previews for a large number of files (e.g. 2714), and try to auto-stack the same set of images based on time interval (e.g. 2 sec), I get the following error,

This error happens frequently.  If I wait until the previews are completed and perform the same stacking operation, it works without error.

I am using version 12.4 of LRC,