I doubt it really matters all that much if you
don't find anything weird going on with the battery itself, the cause of this issue is
almost certainly STILL going to be the battery; whether it's due to old age, poor charging, dead cell/s, loose connections somewhere, or maybe even something else like a blown fuse
somehow draining the battery!

When it comes to a Spyder,
especially a V-Twin with a Magneto Charging System, what you are describing is a dead or dying battery
to a 'T' - the
ONLY thing you haven't described for us yet which is common to this & which most notice is the completely black, blank, or grey lined dash when it fails to start.... :lecturef_smilie:
As for it running fine once you've boosted it, that's common too. On the V-Twin Spyder's with their standard electrical fit-out & load, their Magneto Charging Systems tend to be more than capable of keeping the whole thing working efficiently once you've got the engine & all the computers/electronics up & running - if you've added electronics that push the electrical load past the system's standard charge/run capacity (like maybe added heated seats, clothing, & gloves) or it's just loosing charge capacity, then you
might be lucky enough to run into those blip type issues you mention on your other bike; but more likely, even just
mildly poor output from the magneto will mean the computers simply shut down & shut down everything else along with them pdq after you disconnect the booster! :banghead:
Still, from what you've told us, it really sounds like it's time for you to look at why the battery was dead &/or dying after a good 180 km run like that (or was it??) & if you can, remedy that before fully recharging your existing battery on a charger/maintainer for at least 12 hours or so; or simply buying a new battery if it's just old age on behalf of the battery in there now, & it has given you it's last good charge/discharge cycle!
How old is the current battery anyway?? Do you regularly do lotsa short runs?? 180 km with a half dozen or more shut down/start ups could've been
more than enough drain to kill a battery that was 'a bit tired' to begin with, while 180 km of good highway riding should've beem more than enough to fully charge even 'a bit tired' battery! And what about how often you use a battery tender?? :dontknow: All good/helpful info in tracking down the root cause of your battery's poor condition, but still unlikely to change the end diagnosis/remedy.... :dontknow:
Good Luck! :cheers: