Partly duplicate with https://mods.factorio.com/mod/moon-eneas/discussion/69fd83349c85b7f01950973b, but I think it worth elaborating:

In-game description says that the debris crashing will "pause" after the 80 limit is reached, but even after the amount of the debris is reduced to well below 80, the spawn does not resume. This means that, if the player does not collect sufficient artifacts to unlock Eneas itself before hitting the limit for even once, it will be impossible to do any Eneas research without starting a new save.

Updates: I've investicated your code and find the cause: you registered the event "on_robot_mined_entity" twice: once in events.lua, and once in radar.lua; according to the API doc, the registration in events.lua will be overwitten. As a result, if the player reaches the debris limit, and mines every existing debris with robot, the re-enabling of the debris spawn will not be triggered, and the player will no longer be able to obtain any weathered artifact before going to Eneas. This can be resolved simply by changing the registered event in events.lua to "on_robot_pre_mined".