I have the same problem using precision 5510 + Dell dock, used to have perfectly working 3 monitors setup, which no longer works after the latest update (4.4.0-77-generic).
I can no longer use 3 screen setup, 2 monitors setup is barely working and I often need to reset it after boot, reordering the screen is also impossible. 
I tried that with Nvidia latest drivers, with/without intel profile and the open source driver, got the same results.

here is the log message:

[    3.104821] ------------[ cut here ]------------
[    3.105632] WARNING: CPU: 3 PID: 24 at /build/linux-FyIZxz/linux-4.4.0/ubuntu/i915/intel_pm.c:3675 skl_update_other_pipe_wm+0x16c/0x180 [i915_bpo]()
[    3.106449] WARN_ON(!wm_changed)
[    3.106456] Modules linked in:
[    3.107267]  hid_microsoft hid_generic usbhid rtsx_pci_sdmmc i915_bpo nvidia_drm(POE) nvidia_modeset(POE) nvidia(POE) intel_ips i2c_algo_bit drm_kms_helper syscopyarea psmouse sysfillrect sysimgblt fb
_sys_fops drm ahci rtsx_pci libahci i2c_hid hid pinctrl_sunrisepoint video pinctrl_intel fjes
[    3.109187] CPU: 3 PID: 24 Comm: kworker/3:0 Tainted: P           OE   4.4.0-77-generic #98-Ubuntu
[    3.110085] Hardware name: Dell Inc. Precision 5510/0N8J4R, BIOS 1.2.19 12/22/2016
[    3.110991] Workqueue: events_long drm_dp_mst_link_probe_work [drm_kms_helper]
[    3.111964]  0000000000000286 000000008e1cfc42 ffff8804ab0178b8 ffffffff813f8493
[    3.112876]  ffff8804ab017900 ffffffffc1c95b58 ffff8804ab0178f0 ffffffff81081302
[    3.113779]  ffff8804a36c5000 ffff8804a0d4a148 ffff8804a36c6000 ffff8804ab7dbb78
[    3.114680] Call Trace:
[    3.115670]  [<ffffffff813f8493>] dump_stack+0x63/0x90
[    3.116575]  [<ffffffff81081302>] warn_slowpath_common+0x82/0xc0
[    3.117480]  [<ffffffff8108139c>] warn_slowpath_fmt+0x5c/0x80
[    3.118376]  [<ffffffffc1bb6fec>] skl_update_other_pipe_wm+0x16c/0x180 [i915_bpo]
[    3.119273]  [<ffffffffc1bb7185>] skl_update_wm+0x185/0x610 [i915_bpo]
[    3.120238]  [<ffffffffc1c4842f>] ? intel_ddi_enable_transcoder_func+0x17f/0x260 [i915_bpo]
[    3.121127]  [<ffffffffc1bbaf0e>] intel_update_watermarks+0x1e/0x30 [i915_bpo]
[    3.122038]  [<ffffffffc1c2a701>] haswell_crtc_enable+0x761/0x8e0 [i915_bpo]
[    3.122953]  [<ffffffffc1c15d3e>] ? intel_finish_crtc_commit+0xe/0x10 [i915_bpo]
[    3.123913]  [<ffffffffc01626e4>] ? drm_atomic_helper_commit_planes_on_crtc+0x154/0x270 [drm_kms_helper]
[    3.124831]  [<ffffffffc1c26606>] intel_atomic_commit+0x5d6/0x14a0 [i915_bpo]
[    3.125739]  [<ffffffffc00cbbfe>] ? drm_atomic_check_only+0x18e/0x590 [drm]
[    3.126643]  [<ffffffffc00cc037>] drm_atomic_commit+0x37/0x60 [drm]
[    3.127602]  [<ffffffffc016406f>] restore_fbdev_mode+0x22f/0x260 [drm_kms_helper]
[    3.128511]  [<ffffffffc00ca7ba>] ? drm_modeset_lock_all_ctx+0x9a/0xb0 [drm]
[    3.129418]  [<ffffffffc0166243>] drm_fb_helper_restore_fbdev_mode_unlocked+0x33/0x80 [drm_kms_helper]
[    3.130336]  [<ffffffffc01662bd>] drm_fb_helper_set_par+0x2d/0x50 [drm_kms_helper]
[    3.131249]  [<ffffffffc01661c2>] drm_fb_helper_hotplug_event+0xd2/0x120 [drm_kms_helper]
[    3.132212]  [<ffffffffc1c4132e>] intel_fbdev_output_poll_changed+0x1e/0x30 [i915_bpo]
[    3.133111]  [<ffffffffc01587a7>] drm_kms_helper_hotplug_event+0x27/0x30 [drm_kms_helper]
[    3.134008]  [<ffffffffc1c49cb5>] intel_dp_mst_hotplug+0x15/0x20 [i915_bpo]
[    3.134902]  [<ffffffffc015f46a>] drm_dp_send_link_address+0x19a/0x220 [drm_kms_helper]
[    3.135861]  [<ffffffff810ab5a9>] ? ttwu_do_wakeup+0x19/0xe0
[    3.136767]  [<ffffffff810ab70d>] ? ttwu_do_activate.constprop.90+0x5d/0x70
[    3.137652]  [<ffffffffc015f59d>] drm_dp_check_and_send_link_address+0xad/0xc0 [drm_kms_helper]
[    3.138544]  [<ffffffffc015f608>] drm_dp_mst_link_probe_work+0x58/0xb0 [drm_kms_helper]
[    3.139444]  [<ffffffff8109a555>] process_one_work+0x165/0x480
[    3.140380]  [<ffffffff8109a8bb>] worker_thread+0x4b/0x4c0
[    3.141236]  [<ffffffff8109a870>] ? process_one_work+0x480/0x480
[    3.142074]  [<ffffffff810a0be8>] kthread+0xd8/0xf0
[    3.142907]  [<ffffffff810a0b10>] ? kthread_create_on_node+0x1e0/0x1e0
[    3.143804]  [<ffffffff8183bd0f>] ret_from_fork+0x3f/0x70
[    3.144631]  [<ffffffff810a0b10>] ? kthread_create_on_node+0x1e0/0x1e0
[    3.145472] ---[ end trace 02fae400e85e1562 ]---