I don't think there are any usable Windows log entries which will give more information. Updater.exe is not installable only standalone therefore has minimal interfacing with the PC's OS but check Event Viewer for logs if you want. Regardless, the problem is with the device and error logs if they exist would only tell us what happened to Updater and that we already know: It gets someway into it's flashing attempt i.e. x% erasing before crashing. (In explanation, a region is erased then re-written with fresh data rather than being overwritten). I believe the times "Updating 100%" is seen is mis-reported somehow because the complete flash clearly hasn't happened, not even the initial erase as you still have V5.50 onboard. That "Out of memory" message is probably from using an earlier 32bit Windows.

It seems there won't likely be any success with Updater used like this if your report of "some 100+ attempts" isn't exaggerated. I once restored fw on a stubborn old-style (region only, no visible file system) auto device given to me as a 'write-off' on the 96th try. Every morning i made 10 attempts and on the 9th day the 6th attempt worked, but that's an exceptionally rare case with a different type device with a different problem and usually if the preboot>flashing sequence is properly followed (no operator error - VERY common but not in your case i think) a repairable modern device will be quickly successfully flashed provided other factors like USB cable, proper USB2 port without hub etc. are eliminated.

Time to try something else. First let's see if it can read from and write to the SD card. I doubt it will be able to do that in the normal fashion but it's worth a test try to dump nonvol region 154 before using a modified boot.bin as RGN in combination with Updater hopefully forcing a txt command in sd card.

The test: Extract the attached compressed file from behind the spoiler below to find a folder "Garmin". Place the Garmin folder onto a CLEAN sd card first ensuring the aera is completely OFF then power it on. Let me know if any different screen behavior is noted. If the device turns off or attempts to reboot remove the card. If nothing changes after several minutes remove the card anyway. Browse it and note if there is a new file in the root named 154.bin and even if it isn't there look in Garmin\Updater\1364 folder for a new file named "update.log" and post it's contents if present.
Spoiler:
[Only registered and activated users can see links. ]

If that doesn't work we can try with the modified ramloader next.