Brother printer prints jibberish or nothing

I installed a driver for a Brother MFC-7860DW printer (I downloaded the driver directly from the website because it was not one of the drivers available in the printer-configuration menu). It worked correctly for several days, and then it started printing collections of weird symbols and a bunch of blank pages. It would print them one-sided, even though I had ordered duplex printing. It would do this intermittently, but the frequency has increased dramatically. This would happen regardless of the application I was using.

1. What I expected to happen: The document printing as it appeared on the screen
2. What actually happened: Weird strings of symbols and mostly-blank pages (though sometimes it printed correctly)
3. Steps to make it happen:
a. Open an application (ex: LibreOffice, Firefox)
b. Open a file (or webpage)
c. Select "print"
d. Push okay (to start the printing)

Kubuntu 20.03
Cups 2.3.1-9ubuntu1.1

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: cups 2.3.1-9ubuntu1.1
ProcVersionSignature: Ubuntu 5.8.0-44.50~20.04.1-generic 5.8.18
Uname: Linux 5.8.0-44-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.16
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: KDE
Date: Sat Mar 6 13:21:05 2021
InstallationDate: Installed on 2021-02-11 (23 days ago)
InstallationMedia: Kubuntu 20.04.2 LTS "Focal Fossa" - Release amd64 (20210204)
Lpstat: device for MFC7860DW: usb://Brother/MFC-7860DW?serial=U62702K1N178900
MachineType: Gigabyte Technology Co., Ltd. Z68A-D3H-B3
PpdFiles: Error: command ['fgrep', '-H', '*NickName', '/etc/cups/ppd/MFC7860DW.ppd'] failed with exit code 2: grep: /etc/cups/ppd/MFC7860DW.ppd: Permission denied
ProcEnviron:
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-5.8.0-44-generic root=UUID=22d11d08-d35d-4209-97a6-3faf058446b3 ro quiet splash vt.handoff=7
SourcePackage: cups
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 03/20/2012
dmi.bios.vendor: Award Software International, Inc.
dmi.bios.version: F13
dmi.board.name: Z68A-D3H-B3
dmi.board.vendor: Gigabyte Technology Co., Ltd.
dmi.board.version: x.x
dmi.chassis.type: 3
dmi.chassis.vendor: Gigabyte Technology Co., Ltd.
dmi.modalias: dmi:bvnAwardSoftwareInternational,Inc.:bvrF13:bd03/20/2012:svnGigabyteTechnologyCo.,Ltd.:pnZ68A-D3H-B3:pvr:rvnGigabyteTechnologyCo.,Ltd.:rnZ68A-D3H-B3:rvrx.x:cvnGigabyteTechnologyCo.,Ltd.:ct3:cvr:
dmi.product.name: Z68A-D3H-B3
dmi.sys.vendor: Gigabyte Technology Co., Ltd.