The trigger (besides the grip panels the only non-steel part) on my sample was not properly fitted to the frame and thus did not reset correctly. That doesn’t seem to be an isolated incident. Way down on the following website a user is describing the same issue.
https://www.nationalgunforum.com/semi-auto-handgun-discussion/53800-can-you-identify-gun.html
There are some excellent german websites regarding blank guns. Some of them referred to in the following.
https://www.tactical-dad.com/waffen/schreckschusswaffen/ass-33-6-lacrimae-gaspistole-ohne-ptb/
Below on this website there are 2 videos showing a post WW2 Wadie blank/tear gas pistol using the same operating system and actully ejecting shells.
https://www.tactical-dad.com/waffen/schreckschusswaffen/wadie-automatik-gaspistole-ohne-ptb/
First video has a misfire first as well and he describes lots of sparks coming off the ejection port and in his face. He fired 3 blank cartridges total and at two of them the primer had set back a little and on the third one it was pushed out completely.
At that gun most of the parts are made of zinc alloy including barrel and frame/bolt face. Only some small parts like firing pin, trigger bar, springs are made of steel.
Sadly I couldn’t find any information on the maximum gas pressure. Can’t be that much considering the zinc alloy design and the shells not being supported in any way and have to hold the gas pressure on their own.
Ammunition was made well into the 60’s. Post WW2 ammo has aluminum shells which seem to be more thick-walled than the older brass shells from the 1930’s/40’s.
The pistol apparently needs very precisely dimensioned ammo. Just 0.1mm below and you are getting ignition problems. Just 0.1mm too long and you have difficulties to fumble them in the ejection port.
On the same website there is an article on another pistol (HS4) using the same ammo/principle and there you can see in one of the pics an enlarged gas channel/groove on the left side partially covering the left barrel entrance and the receiver/frame side wall. Thus giving a little bit more gas pressure for the shell ejection.
https://www.tactical-dad.com/waffen/schreckschusswaffen/gas-alarm-pistole-hs4-ohne-ptb/
Some more interesting links I stumbled across:
http://www.poplasnak.cz/b/august-schuler-suhl/
https://www.gas-waffen.de/srs-waffen/august-sch%C3%BCler/
https://www.gas-waffen.de/srs-waffen/august-sch%C3%BCler/modell-33-6/
https://www.gas-waffen.de/srs-munition/8-mm-lacrimae/
http://www.ammo-one.com/8mmTeargascenterfire.html