Likely individual loose connections -- not related. Check all associated connectors and wiring. You can swap EGT leads from left side to right side to see if fault follows wiring or probe.
Soldered wire connections can be very unreliable in a high vibration environment if not done correctly.
10 wraps, 5 and 5 on each side, like a blood knot for joining two fishing lines, supported by heat shrink to prevent flexing.
I am very familiar with all of the different ways to do soldered electrical splices.
I have also repaired a few that fatigue failed underneath wire insulation or heat shrink.
Now a days most professional shops use THESE in situations where a solder splice is acceptable (well restrained and isolated from any influence of vibration).