I have re-imaged my BBB and made the correction to the typo in my overlay file. However, it appears as if I am having the same issue. When I install the overlay in the uEnv.txt file and reboot, I am never able to ssh back into the BBB.
My file is below for your review. I can't seem to find any problems with it, and seem to be stuck again. Do you have any recommendations on how to proceed?
Your very close, just change one "4" to a "1".. 
fragment@1 {
target = <&am33xx_pinmux>;
__overlay__ {
bb_uart4_pins: pinmux_bb_uart1_pins {
These don't match..
pinctrl-0 = <&bb_uart1_pins>;
just change:
bb_uart1_pins: pinmux_bb_uart1_pins {
Then it loads correctly..
uboot_overlays: [fdt_buffer=0x60000] ...
uboot_overlays: loading /lib/firmware/CLOCK.dtbo ...
1607 bytes read in 377 ms (3.9 KiB/s)
uboot_overlays: loading /lib/firmware/BB-BONE-eMMC1-01-00A0.dtbo ...
1440 bytes read in 272 ms (4.9 KiB/s)
uboot_overlays: loading /lib/firmware/BB-HDMI-TDA998x-00A0.dtbo ...
5127 bytes read in 149 ms (33.2 KiB/s)
uboot_overlays: loading /lib/firmware/BB-ADC-00A0.dtbo ...
711 bytes read in 77 ms (8.8 KiB/s)
uboot_overlays: loading /lib/firmware/AM335X-PRU-RPROC-4-14-TI-00A0.dtbo ...
3513 bytes read in 459 ms (6.8 KiB/s)
debian@beaglebone:~$ dmesg | grep pps
[ 0.617569] pps_core: LinuxPPS API ver. 1 registered
[ 0.617576] pps_core: Software ver. 5.3.6 - Copyright 2005-2007
Rodolfo Giometti <giometti@linux.it>
[ 40.470657] pps pps0: new PPS source gps_pps.-1
[ 40.470808] pps pps0: Registered IRQ 115 as PPS source
debian@beaglebone:~$ ls /dev/pps0
/dev/pps0
debian@beaglebone:~$ sudo ppstest /dev/pps0
trying PPS source "/dev/pps0"
found PPS source "/dev/pps0"
ok, found 1 source(s), now start fetching data...
time_pps_fetch() error -1 (Connection timed out)
^C
(i don't have anything wired, so it'll time out)
Regards,