Quick answer: Scale enemy count, health, or damage with the number of players, tune the scaling for each player count, and adjust dynamically as players join or leave.
Spawns not scaling with players is fixed encounter sizing. Scaling it fixes the difficulty. Here is how.
How to fix it
1. Scale encounters with player count
Adjust the number of enemies (and optionally their health and damage) based on how many players are present, so the challenge matches the group size. Fixed spawns make co-op trivial or single-player brutal.
2. Tune for each count
Tune the scaling so each player count feels right, not just a linear multiply — two players may need more than double a solo encounter due to combined power. Test and tune each supported player count.
3. Adjust dynamically
Handle players joining and leaving mid-session by adjusting active and future encounters to the current count, so difficulty stays appropriate. An encounter scaled for four that two players inherit when others leave is unfair.
Catching the ones you can't reproduce
The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.
Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.
This is where a tool like Bugnet earns its place. Its SDK captures every error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.
Reproduce it once with full context and the fix writes itself. The hunt is the expensive part.