The M37 depends on the Slide Stop (#27) to be pulled down out of contact with the rear of the Slide #14 when the gun is fired so that the action can then be cycled.
The Slide (#14 )is what actually cams the Breech Bolt /Block (#3) into and out of battery by way of the pump action arm.
Ithaca 37 Featherlight Parts List | Gun Parts Corp.
The Slide Stop is powered by a small simple wire spring (#28) to engage the Slide Stop. The hammer being fired pulls the Slide Stop out of contact with the Slide and allows the bolt to be opened w/o the need to depress the Slide Stop.
Once the action is again cycled and the hammer is cocked, the Slide Stop is again engaged to hold the Slide in the closed & locked position. So the Bolt is closed and locked and to open the breech the Slide Stop must be depressed to do so or the hammer dropped(fired or dry fired)
If the Slide Stop is not disengaging from the Slide and requires the gun to be bumped on the butt stock,,that wire spring may be broken.
Or..it could be just an accumulation of old oil, dirt, grease that is not allowing the Side Stop to drop out of engagement inspite of having some spring tension on it.
Old guns will do that.
They are a simple mechanism. Likely a simple fix.
FWIW..The mention of the act of banging the butt of stock on ground...
The M37 has an odd way of disengaging the slide op-rod from the 'Slide' when doing just that.
It doesn't happen all the time, nor does it happen very often. But it does occur. I'd call it rare.
The normal TD disassembly of the op-rod from the slide is done by simply sliding the pin which is visible in the loading port to the side and pulling the op rod forward.
On some 37's,,the simple act of bouncing the butt of the shotgun on the ground will do the same. It will disconnect the op-rod from the 'slide' (part#14).
That will leave you with a closed and locked Breech bolt and a Slide handle that is unattached to the Slide and thus the Breech Bolt itself.
Easy to reconnect by sliding the attachment pin to the side and allowing the op rod to reconnect via the pin.
But it is one of those rare things that can occur .