What could cause the wifi to disappear and appear when connecting from mobile phone and some laptops (acer).
Most other laptops/tablets seem fine
How have you configured the data rates? I would set a single mandatory (basic) data rate of 6 or 12 Mbps with all other data rates set to supported. If you set a mandatory data rate other than 6, 12 or 24 Mbps you can experience compatibility issues with some wireless clients.
I would also disable the 2.4 GHz 1, 2, 5.5 and 11 Mbps data rates unless you have wireless scanners or some other legacy style device that requires 802.11b data rates enabled.