bizarro @HP and @Lenovo Intel i5 notebook 4GB DDR3L SODIMM memory problem

bizarro @HP and @Lenovo Intel i5 notebook 4GB DDR3L SODIMM memory problem

got some wierd crucial memory that crashes a HP EliteBook and a Lenovo ThinkPad notebooks

crashes on boot ! and fails memory test ! with the msg "Pa_sed" which i assume means FAILED ! bizarely works fine when "mixed" with a 2GB non crucial ram in a Thinkpad X220 and X410

so the mystery is what is the difference between crucial part no 171994 and no 313550 ?

every other param is IDENTICAL

• 4GB DDE3L-1600 SODIMM 1.35V CL11 (171994  - B.M16FKD)
• 4GB DDE3L-1600 SODIMM 1.35V CL11 (313550 - BJ.M8FP)

???