Using the Control key to pick color while painting doesn't work on UDIMS greater than 1002. It will work on UDIM 1001.
Also, the Clone brush won't work on UDIMS greater than 1001 for the same reason - the Control key doesn't detect pixels on UDIMs 1002 and up.
I've attached a sample scene - a cylinder with UDIM UVs on tiles 1001 and 1002, and textures set up for those UDIMs. The cylinder side is on 1001 and the caps are on 1002.
Steps to reproduce
-Open sample file. Make sure image map "Cylinder_Color" is selected in the Shader Tree. -Click on Airbrush or Paintbrush tool, and control-click the red area on the side of the cylinder. -Next, paint on a white area of the side of the cylinder. -This works correctly - The brush will paint red.
-Next, control-click on the Green dot area on the top of the cylinder (which is mapped on UDIM 1002) -Paint with the brush.
EXPECTED RESULT: The brush should paint with green color., INSTEAD: The brush paints with the red color you picked off the side of the cylinder.
-Switch to the Clone brush. -Control click on the red dot on the side of the cylinder and start painting. -The clone tool works normally.
-Now control click on the green dot on top of the cylinder with the Clone brush and start painting.
EXPECTED RESULT: The green dot is cloned. INSTEAD: It paints red instead (from the last area you picked).