so in the interest of closure, I found what was the issue here... well 2 issues.

so issue 1 was the key intermitantly working, so as someone mentioned to me elsewhere there was a bad batch of chips getting about & would appear that mine may have been either of this batch or faulty in its own right. So I had this Key scanned by another member today with a different piece of kit & it was not consistantly scanning. So appears faulty chip.

Issue 2 the "coil on PCB" type keys i had showing as "unkown Key type error" with AK90, so again had these scanned & they are ID46 type, but upon showing him the add for the keys I bought he saw that they were for CAS2, which the AK90 is not able to program or read so this explains the error i was getting.

so he sold me a replacement chip which worked as expected in the AK90 & the key is now working as it should.
case closed ��