@QuantifyRisk
Hi, welcome to the community.
I think somehow it might be a coincidence that the laptop connects after opening Deco APP. The App itself should not affect the network performance.
Are you able to stably reproduce this issue on different mobile clients?
May I know how many online clients that are connected to Deco?
It is also suggested to change the LAN DNS server to 8.8.8.8/8.8.4.4 to see whether it helps the laptop to get internet instantly when connecting to Wi-Fi.
How to change DNS server settings on my Deco
Thank you very much and best regards.