You identified the problem - not mowing the lawn as frequently as possible. Too much cut grass is accumulating under the deck.
Solutions are: Cut more frequently; cut less than a full width; raise the mower; slow the mowing speed.

Try cleaning the bag with your garden hose. If the bag is clogged up with dust and ground up clippings, then it can't pass enough air through it so no vacuum action. Blast the bag thoroughly with plenty of water and let it dry completely.

Ok will do. Now that I see it said... (lowering the deck)

I noticed we started to have more bagging issues since I lowered the cutting deck. I found out I was leaving my bermuda too long and not cutting enough. So this season I have started to cut more frequently (once a week to 2x a week) and cut with the deck lower. This is when I really noticed our problems...

I will wash the bag out. I did not know the dust would clog the bag like that. How often should I clean it out? After each use?

I noticed the powder coat under the deck comes off a bit more each time I clean the deck. Could the bare metal surface be contributing to the grass sticking and clogging up more then when new? Should I clean it up and repaint it? Should the deck be washed out every time we mow?

thank you again!

Common reasons for under deck buildup of grass are too much grass being cut at one time and the grass being too damp.

Yes, the under deck should be hosed off every time you mow. At season end used a putty knife to scrape off any remaining clumps.

I rinse out the bag about once a month. Be sure to rinse from the outside in.

If you have a pressure washer or can take the bag to a 'spray-it-yourself' car wash, these things really clean a bag. Be careful and don't destroy it and be sure to dry it before using. You can put it on the mower and run it without mowing and the wind from the mower should dry it pretty quick.

It just hit me - you're not getting air through the bag because the blade is on upside down or is worn out, with the rear airfoils worn away. When you put a clean bag on a clean mower, it should balloon out from the wind. That's how you tell it's full of grass, when it stops ballooning. Check that blade.

Ok will check the blade... it has never been removed, so the chances of it being upside down should be non existent. Worn out... maybe? Guess I need to look at a new one and compare. We have a pressure washer at the house for the next few days. Borrowed it along with a dethatcher and aerator for the Bermuda. Will gently clean the bag with it and see if it "balloons out"

Thank you!

"Ok will check the blade... it has never been removed, so the chances of it being upside down should be non existent."
Or maybe.................

Heck, i found a customers lawn tractor had one blade on right and the other one was upside down. No wonder he complained about the blades losing their sharpness! One blade cut it off, and the other one put it back on! ;o)