Marlin-RC8BF-HICi3
Is this a modified flavor of Marlin 1.1.5 for a specific printer ?
My experience with 1.1.5 is from the unmodified core release. I think you said you changed controller at one point?
If not perhaps if you have a spare?
Perhaps load up the raw 1.1.5 from [marlinfw.org] and see if you have the M500 CRC then.
That would prove your ATMega2560 physically is or is not the issue.
Is this a modified flavor of Marlin 1.1.5 for a specific printer ?
My experience with 1.1.5 is from the unmodified core release. I think you said you changed controller at one point?
If not perhaps if you have a spare?
Perhaps load up the raw 1.1.5 from [marlinfw.org] and see if you have the M500 CRC then.
That would prove your ATMega2560 physically is or is not the issue.