Will a DECT phone wireless signal interfere with a WiFi access point signal?

No, if they are operating correctly DECT and WiFi shouldn't interfere with each other.

DECT operates in the 1900Mhz frequency range, specifically 1880-1930Mhz (in some regions up to 1980Mhz). Your Yealink W-series Wireless phones fall in this category.

Most WiFi operates in the 2.4Ghz (802.11b/g/n) or 5GHz (802.11a/h/j/n/ac/ax) frequency ranges. Your AP's fall in this category.

There are also some limited use cases for WiFi in following frequency ranges: 3.65 Ghz (802.11y), 4.9 GHz (802.11j), 5.9 GHz (802.11p), 60 GHz (802.11ad/ay), and 900 MHz (802.11ah), but to my knowledge your Ubiquity UAP Pro AP's do not support any of these rarely used frequencies.

Since the operating frequency of these devices are significantly separated, they should not interfere with each other, assuming they are functioning properly.

If the distance is short enough then anything can interfere with everything. Bandpass filters only have so much damping, even an out-of-band DECT signal can overdrive a reveiver and make it deaf for the in-band WiFi signal, and vice versa.

The frequency separation and spatial separation must work together.

That being said, my own DECT base station and dual band WiFi access point are only 1/2 meter apart, and they both seem to work well enough. YMMV.