Read all of this first, as one of these may stick out to you. The last part is probably the most promising, but wanted to run through some other troubleshooting options first.
1) try a capital T in {Tab}
2). Ensure there are no unidentified spaces anywhere such as {Tab }
3). Try turning off send as hardware keys. I have never had to use that and {Tab} has always worked just fine.
4). Do the same ones always mess up? If so, try copying one of the ones that is working and deleting the ones that are messing up
5)If none of that works, put a Wait(1) between the tabs and other send text. Sometimes PAD just runs over itself simply because it’s moving to fast.
Lastly, is there another field that you can find after and {LShiftKey}({Tab}) back to the field you need?
Good luck!