I have the same Sony and do not have that problem. I have loaded many hi res files at once and haven’t endured what you are saying. Do you have the latest firmware that was released a month or 2 ago? Have you tried transferring the files using the wired Ethernet?
Unable to load files to Sony HAP-Z1ES thru network
I’m having difficulties transferring files—pretty much anything about 96kHz/24bit—into my Sony HAP-Z1ES through a wireless network. Typically, a few files will transfer, but then I’ll get an error message (in the Sony transfer app) saying a file can not be found. The transfer then stops. Any advice is greatly appreciated.