With the Pressure side Polaris the bag "filling up" should not stop the Polaris from moving. It may cause it to slow down or run on its side some or do some other funny maneuvers but that is caused only by the weight of the bag.
That will not ruin your Polaris. The Polaris internal jets, though, can get clogged up if tiny debris from the return (pressure water that feeds the Polaris) is forced into the Polaris innards. The fitting, that is on the end of the Polaris hose has a very fine screen that catches fine debris that makes it through the filter. That screen is vital for keeping tiny debris out of the internals of the Polaris. On this end of your cleaning system, if pressurized water is coming out of the wall fitting then you should look at the condition of the tiny filter screen (and if it is properly in place) and keep it cleaned out (I clean mine at least once a week) or clogging of the jets in the Polaris (or other internal Polaris parts problem) or water leaking from one or more of several places. Also, there is usually a red or blue disc in place in the return wall fitting to regulate the pressure going to the Polaris. There may be some instances where the colored disc is not used but all I've seen (friends) have them in place.
The big dot (white, red, black, blue, etc,.,) on the hose wall fitting is a pressure release that will open up when the wall pressure is more than the Polaris can handle for whatever reason. After a certain amount of time the hose fitting wears out or breaks including the pressure release either not opening or stuck open. Feel for water coming out around the hose fitting and wall fitting to see if any water is coming out at that point.
Another place for water to escape it the free turning joints on hose where each section joins. They wear out and either let water escape and/or become stiff so that the hose doesn't turn freely when it needs to straighten out.
Over time I replace parts of my Polaris including the return fitting, hose fitting, swiveling hose connectors, tails, parts of hose, etc. The little tiny filter screen usually last longer than the hose wall fitting so I have some spares of those; good for when one is lost. You can purchase all of these parts at many Pool Stores or less expensively on line.
Individual Polaris have different drive mechanisms. Some are belt driven; some are gear driven. Please post your model number so that more troubleshooting can be done. :-D
I've had several Polaris since the one with the bigger intake hole came out; many years. I've only had to replace them when my dogs "rescue" and then "kill" them. Otherwise I just replace parts. The one I have now, at least five years old (but more than likely much older), with minimum of 10 hours a day use, almost year round, has external parts that are 1, 2, 3, 4, 5, etc., years old from replacing external parts here and there.
BTW... the drive belt driven Polaris are rumored to have more issues with internal drive issues. Every pool guy/guy I have contact with recommends the gear driven for longevity and less drive issues. Every pool owner, I know, who has a Polaris had the gear drive recommended to them by Pool Builders, Pool Stores, pool service people. Polaris are really popular around these parts. Every person I know, here abouts, with an IG pool, uses Polaris gear driven.
BTW... all parts of the Polaris can be user replaced if one is so inclined. The external shell can even be replaced if one wants a pristine looking pool cleaner.
Posts your model number and there will be good people along to assist.
gg=alice