I received a "private message" (via FT) from an AA agent. [AA does read this forum^]
I supplied my locators for the 3 itns which for which "print trip AND receipt" is missing. Their explanation (which I just received):
(1)One trip was booked via AA-VACATIONS
(2)One is an AWARD ticket
(3)One is wait listed for an SWU.
These don't allow printing receipts (directly) from AA.COM.
[For (3), when my w/l is confirmed, I'll be able to print the receipt.]]
So, in my case, there is NO "glitch".