As first advise I would check for the latest BIOS version and install it. Not sure if this would help, but you cannot do much more. Plus, never ever ever mix RAM, what you experienced is a typical error that is caused by mixing RAM modules from different vendors. What you also cannot achieve for sure, when mixing different RAM module sizes: Dual Channel operation. This requires two same size RAM modules and it is extremely important to run the Ryzen 5500U with Dual Channel RAM configuration. My advise: 1. return your 16GB RAM module 2. get yourself a 2 x 16 GB Kingston Fury Impact RAM kit  3. Remove the 8GB that came with the Dell and store it in the Kingston RAM kit package for later use (do not sell this RAM), you need to swap RAM back to the original 8GB before sending your Dell in for servicing  I have also upgraded the RAM on my Vostro 5415 with this RAM, no issues. I only had to confirm that I have more RAM installed, that's it. The Vostro 5415 BIOS does not have any way of changing the timings on the RAM, so you are better off with RAM that does not require any changes here. [URL]    
I just bought a Vostro 5415 and try to upgrade the RAM following this: [URL] I installed XPG Hunter 16GB 3200 MHz but my laptop wont start because 0xc0000098 windload.efi. The BIOS recognize the 24 GB. Only boot without the extra RAM.
Vostro 5415 RAM Upgrade Issue