...for some reason, when I crafted my response, I wrote it thinking I was on the 1800 page, and never double-checked before posting...for a 122, please disregard the comments...they are valid for an 1800 ONLY!! ...the Ignition is not dependent on Fuseblock in any way in a 122!...now, back to the problem...

General sources of momentary cut-outs of ignition in 122:

Low voltage - Loosing 12V to Ignition switch for any reason.

High voltage - Some issue internal to Ignition Switch-Armored Cable-Coil Assembly (rare) OR Distributor.

If you look around at the obvious (like the back of IGN Sw) and points bolt at Dist and dont find anything, it might be worthwhile temporarily attaching an indicator lamp onto the terminal 30 (Battery Power input) of Ignition switch...it will be lit any time Ignition is ON...then, the next occurrence of Ignition failure, a quick glance at the lamp will tell you if its a low voltage side, or high voltage side issue. You could also connect up a Tach...if it were to drop out concurrent with Ignition failure while other lamp stayed ON, that would point to coil/ distributor area...

Good Hunting!