There is a single object (the "flag") which cannot be destroyed and only one of which can exist. This "flag" grants some benefit to whichever shard it's currently on. For example, energy sources refresh after 275 ticks instead of after 300 ticks, or RCL 8 rooms can upgrade their controller with 1 extra energy per tick (16 instead of 15), or creeps spawned on that shard have 1 free move part (potentially 51 parts), or all sorts of things that might give players with rooms on that shard a slight but worthwhile advantage. Wherever this flag object currently is, is highlighted on the world map.
This would set up an incentive for players to co-operate to try and bring this "flag" to their main shard.
Bug reports, critical problems in the game or site not related to your own code
Update: After i started removing all left over structures in my remotes i am hardly getting any more "Isolate was disposed during execution due to memory limit". Before i removed all enemy structures in remotes my global lasted on average 50-100 ticks before the limit was reached. After i aggressively started clearing all abandoned rooms near me (ive cleared 70+ rooms now), the problem is as good as gone, my global can last for thousands+ of ticks again, mostly resetting when i upload code. This further strengthens the theory that it is the game objects that is a big problem when you have vision in many rooms, not player code. My heap graphs are still very noisy, but it is no longer reaching the limit randomly.
I started clearing the abandoned rooms the 7/19 and did no code changes relating to optimizing globals since then.
After a bit of analysis, it appears that the PTR common module is stuck on an old commit, judging by the fact that CONTROLLER_DOWNGRADE_RESTORE is defined but FIND_TOMBSTONES is not. However, it does have updated versions of the other modules; Tombstone is available in the global namespace.