Length of time to process refund

[snowshoe]

I know the general length of time to process refunds, however, I can't find out if there is an amount of refund that causes that timeline to change.

Most of my clients have gotten refund pretty quickly.  I have a few who are still showing as processing.  Nothing to weird with their returns.  The only similarities that I can't figure out (based on who has called to inquire) are folks that are getting high refund amounts (variety of eitc (not all), ctc, possibly not all eip & claim of different child than last year( as in parents who switch years).  I initially thought it was all returns sent on a specific date (2/15)- but it looks like it may have spread over more days.  They are showing on IRS WMR app as processing, but a month seems like a long time.

Anyone else having similar or have knowledge about what's 

[Just-Lisa-Now-]

Large refundable credits or large amounts of withholding can cause a return to be scrutinized more carefully, especially if they were filed really early in the filing season (when most fraud happens).

Forgetting the 1095A will hang up a return for months before they send a letter, ID Verification is another random thing that causes delays and can be months before the  letter arrives.

[BobKamman]

If your sample is people calling you about large refunds, you need to look also at the people who are getting small refunds and therefore are not anxious about speed.