When I bought my used trailer the previous owner showed me a receipt for having the bearings packed, and the shop had replaced a bearing they said was bad. Two years later I pulled the hubs to repack again, and all four hubs had red grease on the outside bearings, and black grease on the inside bearings. I couldn't figure out why someone would use different grease like that, it didn't make sense. Then I finally realized they didn't use two different kinds of grease, they only repacked the outer bearings and ignored the inner ones so they didn't have to buy new seals. Then lied about the bad bearing, if they had actually found a bad bearing they probably would have greased everything.
That's why I try to do my own work