Diana/RWS T-05 trigger not resetting

[Beeman22]

I have a Diana/RWS 240 (last of the German-made ones, not the new "Two-forty" model). Fun plinker, shoots great, only trouble is recently it doesn't always fire when the trigger is pulled. Cock, load, remove safety, pull the trigger and...nothing. The trigger acts as if the gun wasn't even cocked. The only way to get it to fire is to break the barrel again and cycle it all they way down to re-engage the automatic safety - then it seems to work.  This seems to happen off and on for no apparent reason, even when I am sure to positively complete the cocking stroke. Any ideas what is happening here?

FWIW, the gun is marked T-05, but I was never clear on whether the trigger is the same as the T-05 trigger in the 34's. I was also unable to find any schematics for this gun on Chambers or anywhere else. Anyone else run into this problem or have any idea what is going on here? (or know why know schematics seem to exist for these?)

[Beeman22]

Just found this from a few years ago: https://www.gatewaytoairguns.org/GTA/index.php?topic=161478.0, so it seems like this isn't the first time this has happened, but would be helpful to know what the issue actually is!

[Roadworthy]

It should be the same as the T05 used in the Diana 34.  If I understand your description the gun will cock, the sear latches, and the safety sets normally.  Try turning the trigger adjustment screw (accessed through the hold in the trigger guard) clockwise a quarter to a half turn.  It sounds as though the trigger may be right on the edge of functional.