sdwan_vpn_interface_cellular_feature_template resource is broken in version 20.12

[cmohorea]

Customer upgraded their environment and I noticed that it is no longer possible to edit in GUI Cellular Interface feature templates created with terraform (even new ones created in 20.12 environment). The "Update" button just does nothing. However, manually created in GUI templates are fine, visually exactly same. There must be something missing in the API structure.
Peeking into Chrome console, click on the "Update" button on TF-created template produces this:

TypeError: Cannot read properties of undefined (reading 'dhcp-client')
    at r.setTemplateDefinition (main.d2924ba044764c5bb5d1.js:1:28470381)
    at f.edit (main.d2924ba044764c5bb5d1.js:1:31427404)
    at fn (eval at compile (main.d2924ba044764c5bb5d1.js:1:6404305), <anonymous>:4:548)
    at o (main.d2924ba044764c5bb5d1.js:1:6449408)
    at t.$eval (main.d2924ba044764c5bb5d1.js:1:6395138)
    at t.$apply (main.d2924ba044764c5bb5d1.js:1:6395381)
    at HTMLElement.<anonymous> (main.d2924ba044764c5bb5d1.js:1:6449501)
    at HTMLElement.dispatch (scripts.84facbcccce2db21af62.js:1:42805)
    at M.handle (scripts.84facbcccce2db21af62.js:1:40802)
    at e.invokeTask (polyfills.86357765f7b16f9e949f.js:1:7993)
    at Object.onInvokeTask (main.d2924ba044764c5bb5d1.js:1:31271599)
    at e.invokeTask (polyfills.86357765f7b16f9e949f.js:1:7914)
    at t.runTask (polyfills.86357765f7b16f9e949f.js:1:3072)
    at t.invokeTask [as invoke] (polyfills.86357765f7b16f9e949f.js:1:9125)
    at y (polyfills.86357765f7b16f9e949f.js:1:22174)
    at HTMLElement.v (polyfills.86357765f7b16f9e949f.js:1:22407)

Simplest example of TF resource that is not editable in GUI. Create it and try to change description in vManage 20.12 GUI

resource "sdwan_vpn_interface_cellular_feature_template" "CELLULAR_EXAMPLE" {
  name = "CELLULAR_EXAMPLE"
  description = "Site LTE Internet Transport 111"
  device_types = ["vedge-C8300-1N1S-4T2X"]
  cellular_interface_name_variable = "INT_NAME"
}

Updating via TF works fine.