That's an odd one. Have you tried verifying game files? (close game, right click title in library > properties > installed files > verify integrity of game files)

if that doesn't work, I'd recommend either trying it in multiplayer (local or online) or using the back up saves in the following folder to check if it's an issue with your save file or the game (and potentially to get past that point):
https://drive.google.com/drive/folders/1-9EK5eWBRBEm6zB5QxrTrDgnWEq0JnGg

Please also report it via the link in the following thread, with your save game attached, if you have a minute, so devs and QA can investigate your save file directly. Thanks.

https://gtm.steamproxy.vip/app/1436700/discussions/0/3824173464654653561/

All files passed the check.

Managed to get past that point. It turned out that cannon balls were invisible (and don't even hit you) until I got close enough to the cannon. As soon as you get closer to it, they appear and can get reflected by Pontius's shield as they should.

Maybe the problem with the video drivers, but I got the latest NVIDIA's ones, but then it could be the screen resolution: I have 32:9 monitor. Anyway pretty happy it didn't block my progress.

Sent you a report via a report link though.

Same problem, and reflect only works near cannon (thanks for this)