well i understand you, but
we have an oven pcb, it costed us 15k $ usd to upgrade the controller system to a more modern one, and from an pentium era to i5 8 generation,
but we have tons of issues with the rest, fan blowers, elements etc.. who gotten old and need repairs ...
was it worth it, NO
we had Samsung CP30 and CP45 30 years already, even bought 2 used ones for 12k$ usd to extend the life of thoses we had, the air hoses finally broke down one after the other, air manufold problems, loosing many parts in it .... the list is too long
was it worth it, NO once again
we bought brand new system for 250k $ and all the feeders, for a mere total of half a million to finally get some peace, feeders are darn expensives
at some point you have to decide it's enough, and miracle(s) dont always happen, even with tons of precautions
take some time to evaluate, and maybe its time to modernize the system, the problems are if i understand you, you have only one unit, no backups ? this could be problematic if the upgrades dont go well, you'll losse precious time
thats why we did some buiseness with pcb assembly for a while, while upgrading our systems