I had to replace the x-axis bearings because I used hair spray for so long, that the carriage could barely move. I use IGUS RJ4JP-01-08 now, but only for the x-axis.

After putting everything back into place, I have Z-wobbles now on every print. They look like discrete lines all arount the print every 10 layers or so. It is very strange. I mean, the x- or y-axis belt can be loose but the z spindle doesn’t have play at all. It could also be the extruder overextruding, but it is so regular and a single layer phenomenon. Do you have any ideas?

On the image, there is the faulty part on the right and the part before the problem on the left.

Z wobble is usually caused by a bent lead screw. Is it possible this was damaged during this process?

If not, are the new bearings loose at all?

Some of the Igus “bearings” need to be pressed into an outer shell to compress the bushing to proper dimensions.
Personally I would not use Igus. Go back to the standard bearings.