Exit code 137 means the server was stopped because it went over your plan's memory. This isn't a Minecraft error itself: you need to reduce consumption or get more RAM.
In the GamePanel, check the RAM used just before the stop: if it's hitting the maximum, memory is indeed the cause.
Remove the last mod or plugin you added, then restart: a single mod is sometimes enough to overflow everything.
Pre-generate the world (Chunky): exploring new areas causes the biggest spikes.
Client area, service page, Details tab, Startup command block: choose Optimized (Paper, Spigot, Purpur) or Modpack (Forge, NeoForge, Fabric), Apply then Restart now. These commands leave a memory margin outside of Java.
As a last resort (large modpack, many players): move to a higher plan from the service page, My plan section.
Common errors
- Reinstalling the server changes nothing: consumption stays the same.
- 137 stops even though the displayed RAM stays far from the maximum: open a ticket stating the version and the modpack, we'll take a look on our side.
The full guide, valid for every game, is in the GamePanel fiche: My server stops (code 137) or lags.