The intermittent internet connectivity experienced by users since the installation of the new AP is likely due to interference and attenuation. When wireless access points are placed too closely together (in this case, within 30 feet), they can cause interference, especially if they are operating on overlapping channels. Attenuation refers to the weakening of wireless signals as they travel through obstacles or over distance.
A . WEP is enabled is related to security and is unlikely to cause connectivity issues.
C . There are speed limitations would cause slow performance, not intermittent connectivity.
D . The passwords are not synced would result in connectivity denial, not intermittent access.
Reference:
CompTIA Network+ Certification Guide
Wireless Network Troubleshooting and Design Best Practices