Cimorene

Well, plastic pens are usually fine. It might be something about clear plastic specifically. I found a discussion post on Reddit about it a few months ago when I was looking for something else talking about scientific ways to measure plastic fatigue and saying that after years of anecdotal claims about this from fandom, somebody tested them and proved it is more prone to break than Pelikan resin pens... but again, they're more expensive, and have more delicate nibs. Example https://www.jetpens.com/Pelikan-Classic-M200-Fountain-Pens/ct/4952. I have one of these in an m nib and it's my favorite, but you don't want to press too hard on the nib.

However! For reliable quality and an affordable piston pen? Twsbi is still the way to go. You have to be careful not to over tighten the screw-on joints including the cap (that's how I broke one), but even if it breaks after a few years it is arguably a good purchase. Once you get much cheaper than this a piston pen is usually just not very good. And you wouldn't want the first one you bought to be a Pelikan - the price is too high for an experiment!

But if you want to give stub nibs a try affordably, I would probably recommend a Lamy Safari fountain pen with a stub nib and a converter. You have to purchase the converter and the italic/stub nib separately but it's still more affordable than most other options. Also you will have the other nib if you don't turn out to like stub, and the classic Safari is extremely sturdy, nearly indestructible (the shiny plastic ones are made of ABS aka Lego). It's a pen you can carry with you anywhere (hence the name). I used to have four of them and a bunch of different nibs and I will say that their nibs are good and easy to switch and their converters are quite good too. So I'm really mad at Lamy about the proprietary cartridges but otoh... I can't not use or not recommend them at the cheap price point. The difference in quality and reliability of their nibs vs Kaweco! Read the fountain section of the Safari guide, which links to an article about converters: https://www.jetpens.com/blog/LAMY-safari-A-Comprehensive-Guide/pt/176#LAMY%20safari%20Fountain%20Pens


As for metal pens... It's a love/hate thing. Sometimes I really want one and they are generally more durable... but they have a serious problem with posting the cap on the back of the pen - in tons of metal pens it just won't stay on! And that is practically unusable to me.