Xiaomi 4a gigabit edition disconnections and shielding

Hi all,
I'm having some transient wifi disconnections on a fresh install on this device which disrupt voice calls etc.
I know this device is not properly shielded. Both the above are mentioned in this thread:

I'm wondering what is the impact of lack of proper shielding and whether this has to do with the disconnections.
Is there a DIY way to shield the unshielded parts of the internal board as shown in the photo of the thread? What material should I use? Aluminium?