Unfortunately, Cimbali construction leaves a bit to be desired.
The upper burr mount bolt hole circle is not the same as the burrs.
Notice the misaligned upper burr mounting holes in the right image.
[Note the red index marks to ensure same alignment on reassembly.]

When reassembling, particular care must be taken to ensure the upper burr is concentric with the lower. Position the upper burr so it is centered and gently snug the screws in sequence to maintain center.
If you disassemble the upper burr mount, it is recommended to add a slight countersink on the brass carrier mounting holes to remove machining burrs. If this is not done, it's possible to assemble with the breaking burr out of true. Check the edges of the flanges for burrs as well and remove as necessary.