Yes, I meant return to the first tab. The error comes from print("RAMBar", self.RAMBar, "RAMBar.progress", self.RAMBar.progress)

parseRAM is under class ViewController: UIViewController. I test for it because I wanted to try solving the problem, but it just changed the problem. Originally the problem happened when I changed tabs, now it happens when after I change tab I return to the first tab The logs: STO Backend is up. SUCCESS: statsServerInfo(ok: true, out: 11) RAMBar Optional(<UIProgressView: 0x10320f0a0; frame = (16 192.5; 288 4); opaque = NO; autoresize = RM+BM; layer = <CALayer: 0x281ab4800>>) RAMBar.progress 0.0 STO Backend is up. SUCCESS: statsServerInfo(ok: true, out: 11) RAMBar Optional(<UIProgressView: 0x10320f0a0; frame = (16 192.5; 288 4); opaque = NO; autoresize = RM+BM; layer = <CALayer: 0x281ab4800>>) RAMBar.progress 0.11 SUCCESS: statsServerInfo(ok: true, out: 10) RAMBar Optional(<UIProgressView: 0x10320f0a0; frame = (16 192.5; 288 4); opaque = NO; autoresize = RM+BM; layer = <CALayer: 0x281ab4800>>) RAMBar.progress 0.11 (I change tab) SUCCESS: statsServerInfo(ok: true, out: 10) ServiceTOOLS_Control/ViewController.swift:302: Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value 2022-04-18 18:26:45.461472+0200 ServiceTOOLS Control[2730:247910] ServiceTOOLS_Control/ViewController.swift:302: Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value The error now happens on the print line that you added and right when I change tab.

The line of code that crashes the program is self.RAMBar.progress = Float(response.out)/100, where I try to change the progress bar. self.RAMBar becomes nil when I change the tab and return to the first tab. You can see in the video the line of code becoming red when the program crashes.

I've added a video that explains better the problem

I've put all the infos in a separate answer

Nil comes from self.RAMBar.progress when it gives me the error. parseRAM is called by a timer.

Ok

I wrote all the info in a separate answer

It's my code. I wanted to publish it using GNU GPL / AGPL but I read that you can't.