Slope mode out of control with negative slopes on SB20

I just tried my first GPX to workout converted ride. Once I got used to gearing and changes, everything was going great. Then I hit an odd issue. The first time the app hit a negative slope value, the bike (SB20) went crazy. I didn’t realize it was negative since the app displays rounded percent slope so it just showed 0% (I will be submitting a feature request to display decimal slope values). Resistance spiked and I couldn’t even pedal. I skipped the interval and continued. Everything was good until the next negative. - again displayed as 0%. I skipped and went on. The third time it happened I let it go and shifted to the easiest gearing to see how long it would last. Well it peaked over 600w and I had to skip after 30 seconds. Then it kept happening every few intervals - and not only on the negative slope ones. It even happened on a +4% slope. Finally at the end it was so erratic I had to end the workout. Here’s what the recording looks like:

Does TD not send negative slope correctly? Not that my bike (or any except the Neo I think) can mimic negative. But there’s still watts involved and I’d like to be able to pedal “downhill” for recovery intervals.

I think to be safe we probably should just send zero to trainers for negative values and really most indoor riders would probably prefer .5% or more as we don’t coast much indoors. I am sure we send negative correctly but if bikes don’t support negative then it might do some binary conversation to a big number. I don’t think a lot of people use this feature although on my Neo it works fine but if I stop pedaling the wheel just spins forever with negatives.

We will change this. Do you agree with my .5% thinking?

0% still provides (at least for me) about 50% of my FTP. 0.5% would be even more and that doesn’t really translate to active recovery wattage. I’m sure a workaround would be to just switch to ERG mode for negative slope intervals and enter in an appropriate wattage. But for converting a GPX file to TD would take a bit of additional work to swap all negative slopes to low ERG watts. Not impossible, just inconvenient.

Looking at the results, it looks like it’s not necessarily all negative slope intervals that were causing issues. There were some blocks of multiple negative intervals (3 minutes or so) and the bike was handling those just fine. Is it possible it was just the first interval in a negative block that was handled incorrectly? I think I’ll put together a test workout using a mix of negative and positive slope blocks and see if I can get a consistent result.

You can actually import copy and paste to Excel and create a filter to negative records and update those to 40%/ERG… but still not ideal. Yes if you can clearly reproduce the pattern we should be able to fix it. As I said it works fine on our smart trainers so we can duplicate this.