Deciding on the best 3D part printing method

Hello all. New here sorry if I make a faux pas with etiquette etcMy question is the best method to manufacture parts. The parts in question are based around 56mm square one is approc 25mm tall and the other 120mm. I attach some images of them.I have a 3D resin printer (Elego mars pro 2) and a filament printer (Elego Saturn 3). My attempts at printing them have not gone well. The Resin and the FDM both suffer from dimensional issues. The resin is really bad for that. The one thing I need high accuracy eg 0.1-0.2 mm.Currently I use JLPCB 3d printing services and they produce very nice parts but in the long run they will be expensive to use full time.I looked at getting them machined out of Delrin but even the material is expensive. I looked at casting them from resin but even that has issues with shrinkage and they would need post drilling etc So my question what is recommended. Is it possible to dial in a 3d resin print to get repeatable accuracy?They parts need to be ideal stable to 60+ oC and waterproof and good for many years with water inside. They will not be exposed to sunlight etcThanksTim