Do you ride near saltwater? I've seen bearings lock up overnight riding on beaches. Less common further away from the coast.
The bearings are supposedly sealed for life although they allow things like water dirt etc to get inside and cause trouble.
Option 1 Buy new bearings even have a extra set that you put in the kite bag or board bag. (very handy if going on trips to the coast that don't have kite shops.
Option 2 you could try this product the only one i've seen that uses an actual metal needle to get into very tight areas. https://www.sfrcorp.com/product/protect ... ion-oiler/
Option 3 I've heard of people taking the bearings out and soaking them in a motoroil bath overnight also heard they did this even if the bearings weren't locked up but did it any way cause they were in a salt water zone. I think its kinda messy and wouldn't problably do that myself bearings are relatively cheap.