Quick answer: Construct 3 Photon multiplayer event payload exceeding the 64KB message limit? Photon caps per-message; chunk or compress.
Game state broadcast hits 80KB; Photon rejects the message.
Chunk the message
Split state into 32KB chunks; clients reassemble. Slightly slower; works.
Or compress
gzip the state before send. 3-5x compression typical.
Use room properties
For state that persists across joins, room properties (which have higher limits) work.
“Network messages have limits. Photon's are below most other systems.”
Plan for Photon limits at design time. Late retrofitting is painful.