The latest version of the mod has a bug in the Land Claim system, causing the credits to be subtracted when picking up power poles, rather than refunded.

Fix - edit systems/land-claim.lua

Line 43 reads AddCredits(entity.force, claim.cost * -1)
Should read AddCredits(entity.force, claim.cost)

Do you use this mod for 0.16?
Anyway, I fixed it and optimized events https://mods.factorio.com/mod/m-multiplayertrading

No, I used it for the latest version of Factorio (1.1.38).

Also, after you posted the link I noticed that the error pertained to the 0.5.0 version, not this one. I missed the fact that the new one has a separate page, as google directs to this one by default.

Anyway, great idea with that mod.