Optimus Polaris Optifuel stove

Does not sound like proper operation.  Was the canister inverted by any chance?  That could cause some sputtering and flames but it should not go out.

Is it still under warranty?  You might just return it.

One test would be to try liquid Coleman fuel. If it has been used a lot, did it not come with a magnetic gizmo to clean the feed to the burner. That might help.

I owned the Optimus liquid fuel only version of this stove and it worked like a charm for over a decade.

If Hikin’ Jim were here he would tell you that the burner design dates back to the Primus One that the turn of the century arctic explorers used.

Cheers

Assuming you read the manual. It seems as some flaring up is normal even with isobutane when the stove is cold in a couple of videos I saw about it. I don’t have first hand experience with it.

Also, even though the canister can be inverted, you need to start the stove with it upright and once the stove is warm, you can reverse it.