I had wrt1900s replaced them all. They had a bad tendency to \”drop\” connections or freeze up pretty frequently. While using a competitors in the same area with the same traffic (testing fro environmental interference) ran flawlessly. Sucks that the router workers better with someone else\’s firmware/software combo than the actual manufacturer. Linksys was a name I stood by but after CISCO did the horrible job of trying to experiment with consumer grade hardware and then left the WRT1900 I think just came out of the box flawed. (still does).
Borrow a router from and friend and test it before calling judgement on anything but I am willing to bet replacing that wrt1900 with something different will fix your woes.
In a potentially congested area, you need to determine how many other networks are coming into your apartment, and what channels they are using.
This can be done with free software such as inSSID. Once you have run that, you can see what channel the other networks are on, and you can choose another one (hopefully).
On the 2. 4 GHz band, remember that there are really only 3 channels to choose from, namely 1, 6 and 11 due to channel bonding. In my experience, it seems that many routers seem to default to channel 1, and you may be better off on 6 or 11. The other solution is to upgrade to AC as it is less congested and you are more likely to find a free channel.