Additional postage needed from USPS

[pakpooty]

Not sure of anyone have had this happened but I recently had some PWE returned to me saying additional postage needed of $0.46 cents?

I have shipped hundreds of the same envelope with PWE $0.97 with no issues and them being delivered. However I've received 3 today saying additional $0.46 cents. Why? All are the correct size envelopes, under 2 oz and less than a 1/4 inch. Why is USPS sending these 3 back when they fall under the guidelines? Also why did the hundreds and hundreds I've shipped before had no issues which were delivered?

I swear USPS has been so bad with consistency on not only scanning and updating tracking but also delivering them on time. Not this with saying additional postage needed. I measure and weigh all my envelopes so it should be an issue at all. 

It's costing be additional shipping I have to pay now for another label, additional supplies I need to use and refund I have to issue because of USPS incompetence. eBay and USPS needs to fix this for sellers.

[fm2000]

The envelopes are non-machineable, the 46 cents is the non-machineable surcharge. ESE must be machineable (there is no non-machineable option when you buy ESE, unlike regular letter mail... I wish there was, but I digress...)

Do the problem ESEs have cards inside top loaders inside? If the envelope cannot bend, and they can't with top loaders, they can arrive postage due for the non-machineable surcharge.

eBay is not as clear as they should be about this. ESEs must be bendable, and there should not be top loaders inside.