Thanks for the info.
You're using UEFI Clover boot, right? I ask because this problem only happens with UEFI Clover, not legacy boot Clover. It is workable for me to install both UEFI Clover and legacy Clover and boot using legacy when I need to boot w/o caches, but it is kind of an ugly solution (when updating Clover, I need to run the Clover installer twice, be careful with the config, etc). I'm going to put the HDD for Windows back in this machine and do a BIOS upgrade as I think there is one available (or maybe use USB stick). I wonder if there is a difference between BIOS versions here. And I've got some other things to try wrt HFSPlus.efi (trying to extract the one from my MacBookAir6,2).
No problem and yes, mine is setup as UEFI. I don't have the legacy version installed at all. That is very strange I must admit. You're not the only Envy user I've spoken with who had issues with Clover UEFI. Hell, initially, I had several myself but I'm pretty sure those related to Clover not having support for my newer hardware yet. Hopefully, your issues get resolved soon.
It's worth mentioning that my system is set to boot in legacy mode and not in UEFI as it defaults. Since UEFI takes priority during bootup, Clover loads first like I want it to anyway so it works for me. This setup allows me to boot my non-UEFI Windows install. You might want to look into testing it if you haven't already.
I need to try a BIOS upgrade too since I noticed an irritating bug that causes my new Azurewave WiFI/BT card to fail to start Bluetooth properly if it is disabled using the F12 switch during a session. I don't believe you've done much BT testing last I checked but could you test out yours if possible? It occurs with OS X and with Windows. In Mac, the BT icon is visible at boot and all options are available but if you try to connect a paired device, it will never connect. The only fix I've found involves resetting the BIOS to it's default settings and manually changing them back to preference and booting again. It is really annoying.