Hi Steve,
Do you understand that the ICOM IC-7300 has a CI-V port and a USB port. You didn't mention which method you were using. Access to the CI-V port would be through a cable with a USB-to-Serial adapter. Mine has a CH340 chip which uses a Windows driver from WCH.
I would speculate from your reply that you are connecting via the radio's USB port. That being the case, I went ahead and disconnected my Raspberry Pi to get it out of the way and then hooked up my Windows laptop to my IC-7300. I then upgraded CHIRP to the latest CHIRP daily build. My laptop has never been hooked up to my IC-7300 before, but it has programmed many radios using a programming cables that were manufactured with the Silicon Labs CP210x chip. That being the case I let Windows use the Silicon Labs driver that has been previously installed and didn't bother with installing the one that ICOM hosts on their website. I used Device Manager to determine that the IC-7300 was assigned COM5.
My first attempted download from the IC-7300 resulted in the same errors that you experienced. Since I was using the same USB cable that I use for FT8 I knew the USB cable was OK and I assumed that the SilLabs driver was OK, I speculated that the problem most likely was do to an incorrect setting in the IC-7300. I went through the IC-7300 settings one-by-one and decided it might be...
MENU -> (2) -> SET -> Connectors -> CI-V -> CI-V USB Port and changed its selection to *Link To [REMOTE]
*
After making that change, CHIRP read the memories from the IC-7300. I had never enter any memories before so all 99 were empty. I was able to key frequencies into CHIRP and they would show up in the IC-7300. Unfortunately if I keyed frequencies into the IC-7300 they didn't automatically show up in CHIRP. I had to close the IC-7300 tab and read from the radio again. So it appears that CHIRP's ICOM IC-7300 driver only offers very minimal support, it does work.
If you had to change CI-V USB Port to get this to work like I had to, don't forget to change it back when you are done. My digital modes won't work until I do.
Jim KC9HI