Hi.
I just got the following crash: https://prnt.sc/O4yd2RqLEb9v
The crash happened after I tried to list the same item twice with different quality levels in a requester chest.

I just tried to replicate this by adding a request for Wooden Chest (common) to a requester chest and then a request for Wooden Chest (uncommon) and it didn't crash.

Can you give me more detail so I can replicate and fix the bug?

Are you maybe using a mod that changes/adds rarities?

P.s.: Nice avatar. Big train user I assume?

Yes,
I use this mod: https://mods.factorio.com/mod/QualityPlus
And I tried setting Normal and Normal+ Quality Constructrons. So in this case an item from this mod: https://mods.factorio.com/mod/Constructron-Continued?from=search
If it's easier for you, I can also send you the save.
P.s.: Yeah, I like using trains a lot but I think trucks are nicer, especially in OTTD. That's why I'm eagerly waiting for the 2.0 update of Klonan's Transport Drones Mod.

I added support for custom qualities, such as those from the mod you mentioned. Please let me know if you run into issues!