@Handle9 The mix of random access points and repurposed routers will be more or less the reason for things not working too well. The Edgerouter won't be causing the Chromecast to not work, it'll be due to this mix of access points. Your network is actually quite messy.
Try a single Cambium along with the Edgerouter to diagnose the Chromecast issue. If that works, then you've got a device not playing nice. Add devices until you see the Chromecast not working. I see no reason why the Edgerouter would be causing this.
If all out fails then post your Edgerouter configuration on here omitting personal details from it. But like I say - there shouldn't be any reason for your ER-Lite to be doing this.