Machine moves and exceeds Soft-Limits after Homing

[xsrf]

Hi,
I bought a Sculpfun iCube Pro Max and it runs Grbl 1.1h with this default config:

Output of $$

$0=10
$1=25
$2=0
$3=0
$4=0
$5=1
$6=0
$10=1
$11=0.010
$12=0.002
$13=0
$20=0
$21=1
$22=1
$23=3
$24=200.000
$25=3000.000
$26=250.000
$27=3.000
$30=1000.000
$31=0.000
$32=1
$41=0.000
$40=0.000
$100=80.000
$101=80.000
$102=250.000
$103=100.000
$104=100.000
$105=100.000
$110=10000.000
$111=10000.000
$112=1000.000
$113=1000.000
$114=1000.000
$115=1000.000
$120=300.000
$121=300.000
$122=1000.000
$123=200.000
$124=200.000
$125=200.000
$130=130.000
$131=130.000
$132=200.000
$133=300.000
$134=300.000
$135=300.000

It comes with Limit-Switches at the bottom left, so it supports homing. I understand that soft limits are disabled because often the laser is positioned manually. However, I wanted to turn soft limits on, so I set $20=1.
However, now something potentially destructive happens.
When I home and the issue G0X131 I get Soft limit error. When I then issue $H, the machine Homes and the moves to X131 (also displaying machine coordinates X131) and slams into the end. I can then jog left to X128 but X127 would give me Travel exceeded error. I can jog right as far as I want, hitting the end.

Despite $130=130 the actual soft-limit sits at X127. I guess this is due to the Homing back-off $27=3 so the actual valid moving range is from X-3 to X127.

Here is the output of LaserGRBL doing this:

The machine sits at MCO X134 at the end (slammed into the end few times).

Obviously the firmware is potentially modified by Sculpfun, but I thought I'd report this here anyways.
Am I missing something?

P.S. I noticed that when I set $27=2 then after Homing the machine sits at -1,-1. So changing $27 doesn't affect the lower left end of the moving range. It must be somehow baked into the firmware that the endstops sit at -3,-3? Not sure if this is relevant.
Edit: Might be relevant. The fact that I could jog left 3mm might be because of this. I tried setting $130=100 then G0X120 (gives soft limit) then Home homes and moves to X120 and I could still Jog left 3mm until I get travel exceeded. So Jog still thinks I was at 0,0 after Homing.