Yup. Just happened to me and it SUCKS.

Would be great to see this one fixed!

This must be fixed, it ruins so many mods and missions.

Serious problem which has cost me several times when I try to swap a situation weapon back and forth. Please deal with this whenever you can.

think i read some where its a arma 3 issue not the mod?

Yep serious issue for persistent missions. I don't see it in between logins or restarts, but I have to remember to remove all attachments before storing a weapon in backpack and logging out.

Hello,

is this issue still valid?

Thank you

Unless you recently made a change yes it is. Mainly a problem with persistant missions which record your equipment, but has bitten me immediately every now and then as well.

Hello,

I was unable to reproduce it on Steam Stable. All weapons kept their attachments when put into backpacks/inventories. Could you please upload a simple repro mission and provide repro steps? It would help us a lot.

Thank you!

I play the Breaking Point mod a lot (http://www.thezombieinfection.com). This issue is extremely prevalent as the game play of the mod relies heavily on storing weapons in crates/backpacks. I do not always see this bug, it's more of a risk of losing the attachments if you place a weapon in a crate or backpack. I do not typically lose the attachments when said weapon goes into the crate, but when I pull it out. Also, if the server restarts with said weapon still in the crate or backpack you will lose the attachment(s).

I do not have a mission to reproduce this, but I'll see if I can get a video of this happening.

Thank you, but it is essential to reproduce it on Arma without any mods. These can be the cause of trouble. Thank you.

I can't reproduce this on stable with no mods.

This isn't an actual inventory issue. This is about the ability to script-add weapons with (custom) attachments into containers.
These people were probably all playing mods that save player inventories.