Update on my roof: it indeed suffered from the exact same issue as gmuirnz mentioned above: cables almost cut off in the roof loom.
In particular, the "convertible top latch closed sensor" did not give any signal. I could see this in SDD under measurement also.

I soldered the connections and reinforced them. I ended up soldering 3 of the 6 wires. Result: my roof is fully working again.

Additional information: How to diagnose the sensors using a multimeter:

1. Convertible top lid compartment cover piston out sensor (a.k.a. tonneau panel latch sensor): this sensor can be checked by disconnecting the connector to it:
- supply cable, located at the far left side under the tonneau cover: with "contact on", it should read ca. 12 V between the terminals
- cable to the sensor: it should read ca. 1-5 MegaOhm between the terminals

2. Tonneau panel switches are wired in series
- supply cable, located at the far left side under the tonneau cover: with "contact on", it should read ca. 12 V between the terminals
- cable to the sensors (in series) it should read indefinite when at least one of the contacts are open, it should read zero Ohm

3. Front latch close sensor and Front latch open sensor: on the roof, under the cover panel, there is a connector with 4 terminals, 2 for each sensor
- the brown cables go to signal ground,
- the coloured cables are the signal feed cables
- with "contact on", it should read ca. 12 V between the each of corresponding coloured and brown terminals.

4. How to diagnose a possible cable loom damage:
- the roof functions partly, but not completely, resulting in a "roof not latched" error
- the roof will not open at all or not close at all

If one of the power supply cables to the roof latch motor is cut off, then the roof latch motor will not work at all.

In all cases, it is best to identify the cable loom as pictured above for a flat spot and cut it open there for diagnosis.

 

Could be a "sticky"?

 

My searching led me to this item on eBay. It appears to be the HAARTZ German top with glass window with defroster connection for $800. Anybody found a better deal?

https://www.ebay.com/itm/295485385379

 

I bought that top and returned it. It's OK if you want to sell your car. It's cheap for a reason. There's more to a new top than just the fabric. You get what you pay for.

 

May I ask what deficiencies you found? I am a new X150 owner, so I am not aware of the pitfalls.

 

Sorry, I don't remember the details. You should just buy it. It's returnable if you don't like it.