Arria 10 DDR4 SODIMM calibration fails occasionally. How to remove this bug?

Probably I should clarify. We now have more than one PCB we have 180 same boards. On some boards, bank B is calibrated stably at 900 MHz; on another number of PCBs, bank B is not calibrated continuously. sometimes yes, sometimes no. On the third, it does not calibrate at all. Today we decrease the frequency at the input oscillator so that the total became 600 MHz and those banks that were not calibrated are calibrated. It is very likely that in one batch of PCB there are differences in impedances on data lines and memory addresses. FPGA design is always the same.