I encountered an issue recently where the four Cisco Aironet wireless access points deployed at a bus depot in South Yorkshire were not providing sufficient coverage and data downloads from the buses not completing, despite all tests showing it should be excellent.
After some frustration I eventually discovered that some (all?) TGX150 ticket machines are equipped with US and not EU wireless chipsets which means they only work with channels 1-11 and not 1-13 as one would expect in the UK.
If you have having issues with your depot wireless LAN and TGX150 data download I would recommend checking what channels the access points are configured to operate on and adjust accordingly.
I just came across your blog and I am having the exact same issue with HP access points and the TGX150 ticket machines. have you any more info on how you resolved the issue? I have alot of access points which are setup on a range of channels all the way up to 16. I’m seeing the ticket machines connect to a access point and then when the bus moves around the yard drop off and not connect to another AP until it is in range of the original AP again.