It turns out that the loose grounding strap was not the whole fix. In fact the whole fix is yet to be discovered. I have learned from the dealer that 2018 and 2019 Tahoe / Yukon / Esky's more or less all have a passive entry / remote start issue - Some worse than others. The dealer can't explain why it's only these models, other GMC vehicles work just fine. The last attempt I made at fixing the issue was to have the TSB performed which replaces the driver side receiving unit. This may have resulted in a small improvement, but the system still is not what it should be and not what my previous 2016 Denali provided. It's frustrating!