Quick answer: Construct 3 Photon room state hitting the 1MB property limit? Compact state representation or use sub-rooms - photon room props can't exceed the cap.
Save state in room properties; hit limit at 1MB. Players can't sync past that scale.
Compress state
JSON stringify; gzip; store as base64. 3-5x compression on typical state.
Or split across rooms
Game state in main room; per-area state in sub-rooms. Each below the cap.
Store offline
Server-side database for full state; room properties for delta. Photon for transport.
“Network state has limits. Plan around them.”
If your game has growing state, model the limits at design time. Retrofitting compression late is painful.