What have you already done recently? Your current BIOS is from April 2017 so I'm guessing you're not referring to updating it.
Are you using the same memory you had when those crash dumps happened? I ask because they suggest faulty memory. None of the current diagnostic tools are sufficient for testing DDR4, in my opinion (memtest86, Windows Memory Diagnostic, etc.) I've seen too many instances of them saying the memory was okay only to find out later a DIMM was bad. The most reliable method with DDR4 is to use the system as you normally would with only 1 DIMM installed to see if the computer becomes unstable with one vs the other(s).
You wrote that you suspect the HDD. Have you run a full diagnostic of the drive? Seagate SeaTools will usually work for testing a Toshiba HDD. It's best run from bootable media so the whole drive can be tested "offline". SeaTools is included in boot discs such as UBCD and Hiren's if you have those or you can use the instructions here to create SeaTools specific media.
