tbh it sounds like either you did something wrong with the original xboxes or the modder didn't do a very good job, i had a modded original xbox and it lasted until i stuck it away in the loft (it probably would've lasted longer, but i think it got thrown out at some point).
unless you mean a modded original xbox 360, many of the original xbox 360 models had a terrible build quality especially the Xenon models, back when the JTAG mod was first released so many people botched already dead 360 consoles back to life so they could perform the JTAG hack and sell them at a premium, there were inevitably going to die again in a very short amount of time but with the original JTAG hack being limited to low dash version consoles there was an abundance of dead consoles that hadn't been online for a long time sitting in peoples closets