Flex player leaked memory like a sieve. After one day or so it would hang the computer. Maybe it was wrongly written, but leak it did. I have experienced it first hand.
Maybe it was the standalone flex player instead of the web Flash player?
I don't know about a standalone Flex player, I don't think such a thing existed. Maybe you mean standalone Flash player. I didn't use Flex components. I coded in pure AS3. I had critical business code that ran nonstop for years on end in AIR on dozens of deployments without memory leaks. Again, I think that badly written AS3 code (or bad components) could definitely take down a player fairly quickly. Garbage collection required you to track and clean up weak references, but it's the same thing in Javascript. You had to know the lifecycle of your components and what you were doing.
It is possible I was holding it wrong. I do not doubt your experience, but it was very easy to write things that leaked memory in Flash, and it was impossible to remove those leaks sometimes. I was part of a project where a lot of effort went into removing references etc and it was still not working. We had to have 2 instances restarting each other. It was a mess. Maybe we can agree those were "bad components".
I blame the runtime. The quality of the code was good. It was not normal.
A few sources of people complaining about the same, some from hn with the same solution I had to adopt, some from CVE, some from users:
