Sometimes crystal cases are grounded and sometimes not. Why is this?
I find this hard to believe.I have experience with small cylindrical 32 kHz crystals, sometimes they will not run if shell is not grounded.
So was i when first time stucked to non-working 32 kHz crystal several years ago. I struggled with this crystal about week until i accidentally discovered that crystal shell grounding fixes the poblem. Not all 32kHz crystals behave similarly, even with same MCU. I have an Meterman/Amprobe simple contact thermometer which worked for years until stopped. I changed CR2032 cell but the thermometer was starting and then resetting shortly. After connecting crystal can to common wire it started normally and is in good shape today too. I have'nt found good explanation for it but i leave now for this type crystals small grounding area on PCBs.I find this hard to believe.