Would a recompile of MapSource 6.16.3 fix the map crashes for Zumo owners?

Recompiling MS on the face of it would be a cheap quick fix.

Once you take into consideration that it almost certainly won't compile clean first time, will need mountains of regression testing, will need a complete review of the various licensing schemes affected, will need protective code to exclude incompatible devices and will encourage those hanging on for grim death to the now defunct application to imagine that their dreams might come true one day, if they only wish hard enough, I think it unlikely that Garmin will comply.

I have neither North America maps not a Zumo 66x so am unable to assist further.

From what I understand, the current BaseCamp 4.4.2 is not usable for Zumo 66x users. MapSource (as a recommended workaround by your CSRs) started crashing with the 2014.10 maps. If there was a database structure change at that time, would a simple recompile of MapSource use the current structure definitions and stop crashing.

Test case for MS: use the Route Tool to make a route from Newport, TN to Johnson City, TN. It will crash with the 2014.10-2015.30 maps.

For me Mapsource works fine with 2015.20 or 2015.30 Just ran a route two days ago and unloaded to my Nuvi 550. Made the same route in BC 4.4.2 and it loaded in my 2497LMT. The only difference I saw was the 2497LMT added an hour and half to the travel time. The 550 had the correct.

For me Mapsource works fine with 2015.20 or 2015.30...

MapSource 6.16.3 has known issues with newer City Navigator North America & Europe maps in some areas. I don't have a problem where I live but others do. I have personally confirmed that a problem exists. It's all buried in a thread somewhere that I can't be bothered looking for right now.