My paratrooper repeater developed this sort of problem. I would call it failure to cock. That is the process of breaking the barrel until the piston engages upon the sear ( part of the trigger mechanism) ready to be loaded and fired.
There can be many reasons but in my case a pin within the main mechanism wore out and the looseness stopped it cocking.
More often the sear can wear or springs can weaken. Hopefully someone can offer further advice.
The more I think I know, the more I realise the less I know.