Precision 5510, U3014, DDM failing

Hi all,

DDM previously worked fine with my U3014 monitors attached to my 5510, but has stopped working. The DDM diagnostic dump shows a collection of failures with I2C communication:

11:42:38.887...Starting enumeration
11:42:40.476...1. DEL4081.P1V6N364400L on Intel(R) HD Graphics P530
11:42:40.477......Monitor assignment = 1
11:42:40.478......Adapter name = \\.\DISPLAY1
11:42:40.479......Monitor name = Dell U3014 (DP)
11:42:40.480......Vendor ID = 8086
11:42:40.482......GPU driver = igdumdim64 26.20.100.6951
11:42:40.485......Flags = 00000005.00000003
11:42:40.488......Display tag = FEE2B580
11:42:40.490......Monitor number = 1
11:42:40.491......Monitor handle = 046F0769
11:42:40.492......Raw EDID = 00FFFFFFFFFFFF0010AC81404C30303417170104B54028783A1DF5AE4F35B3250D5054A54B008100B300D100714FA9408180D1C00101E26800A0A0402E603020360081912100001A000000FF00503156364E3336343430304C0A000000FC0044454C4C2055333031340A2020000000FD0031561D711C010A20202020202001FE
11:42:41.170......Error: communicating via DDC/CI (0xC0262583) = An error occurred while receiving data from the device on the I2C bus
11:42:41.174......Error: failed to obtain output mask from display driver
11:42:44.356......Error: communicating via DDC/CI (0xC0262583) = An error occurred while receiving data from the device on the I2C bus
11:42:44.360......Error: failed to obtain output mask from display driver
11:42:50.072......Error: communicating via DDC/CI (0xC0262583) = An error occurred while receiving data from the device on the I2C bus
11:42:50.075......Error: failed to obtain output mask from display driver
11:42:50.076......Discarding unsupported display: DEL4081.P1V6N364400L on Intel(R) HD Graphics P530
11:42:50.078......Status = 00000000

Any ideas on how to fix this?  The monitors are attached via DisplayPort with a TB16 dock (yeah, most problematic piece of hardware Dell has ever sold).  The DDM version is 1.40.1942 (20 Jan 2019), and all system drivers (Thunderbolt, dock, dock firmware, system BIOS) are up to absolute current (so as to correct the usual raft of other problems with the TB16.)

Thanks in advance.

-frank