MPC1000 w/ JJOS 128SP Program Change issues

Hi folks, I'm having trouble changing programs (patterns stored in Erica Synths Bassline DB-01) using MPC1000 w/ JJOS 128SP. Emailed Erica Synths but they haven't seen similar issues from other users so I'm trying my luck here...

My MIDI chain: MPC1000 (MIDI OUT) -> (MIDI IN) DB-01
MPC is only sending MIDI clock, start/stop transport messages and program change messages to DB-01 only,
DB-01 is playing patterns from its internal sequencer.
DB-01 supports "MIDI Instant Program change" aka MIP:
- If MIP = ON, DB-01 should change pattern instantly upon receiving PC message
- if MIP = OFF, DB-01 should wait until the current pattern is finished playback before switching to next pattern.

Issue #1:
If MIP is set to ON and I hit PLAY on my MPC1000, my DB-01 will always double trigger the first step of the pattern then play the pattern ~1 step too late (timing offset ~ 1 step), similar to a MIDI lag. This will happen regardless if I switch sequences with different PC values or not. It just always double trigger the 1st step of its pattern then lag behind MPC's playback.

Issue #2:
Let's say my MPC is playing a MIDI project with 2 sequences. Sequence 1 points to Pattern 1 in DB-01 and Sequence 2 points to Pattern 2.
If MIP is OFF and I switch sequences from 1 to 2 in MPC, DB-01 will play 1 extra loop of the Pattern 1, then change to Pattern 2, i.e. program change happens 1 pattern length too late (timing offset = 1 pattern length).
If MIP is set to ON, Issue #1 will happen regardless if the MIDI sequences are switched or not.

I have tried the same test with Dreadbox Typhon and Nymthes and they both work perfectly. When I switch sequences with different PC values (different preset patches), no lag or latency or double triggering.
MPC1000 has been my main sequencer and sampler for more than 10 yrs and I've never encountered this issue before...

Anyone?
I found this MPC forum post from another user in 2019 describing a similar PLAY START button bug and sync'ing issue with Roland TR-8S: viewtopic.php?f=38&t=212623

No one seems to care about this and I've been told it was the TR-8S, "good" to hear it happens on a different machine too. That means it isn't the TR-8S but something about JJOS. I posteddetailed SysEx dumps of what is going on, but it's not going to get fixed it seems.

My workaround was not to send PC data to the TR-8S. Yeah it sucks but that's what it is.

Hi kdrone, I'm currently exchanging emails with Murai-san of JJOS. No real breakthrough yet but will keep you updated in this thread.

Have you considered using something like a MIDI Solutions Event Processor to convert MIDI CC sent from your MPC into PC data?

Example here: https://www.midisolutions.com/chapter2.htm

kdrone wrote:No one seems to care about this and I've been told it was the TR-8S, "good" to hear it happens on a different machine too. That means it isn't the TR-8S but something about JJOS. I posted detailed SysEx dumps of what is going on, but it's not going to get fixed it seems.
My workaround was not to send PC data to the TR-8S. Yeah it sucks but that's what it is.

Welp after trying out 3 different 128XL test builds (128SP has been discontinued) provided by Mirai-san, we still couldn't resolve this issue completely. With some builds, it will sync correctly once in a few tries but never consistent. With other builds, the issue got worse. It's just simply too difficult to debug when Mirai-san cannot reproduce the bug on his side.

I've since exchanged my DB01 with Sweetwater for a new unit and it still runs into the same issue. My next step is to try my old Octatrack to see if I can reproduce the bug.