Definitely caused by not letting the bolt slam forward on its own.
However if while handling the gun you accidentally knock the bolt handle back a little bit then this will also prevent the firing pin from striking correctly.
If it happens again look carefully at the primer on the cartridge - it may have a very small mark on it.
Not had any other problems with this gun except it doesn’t seem to like 65mm shells of any load, so can only have one in the chamber and one in the magazine or it won't cycle every time