The Intec controller works OK up to the point when I start rumble,
sometimes the motor runs some times it doesn't. I am using SDL2's
'testhaptic' application.

That's not quite true. Both SixAxis and Intec lock up machine with
'testhaptic'.

Using 'testrumble' the SixAxis works multiple times, Intec locks up
straight away (sometimes starts motor).

USBMon shows Testrumble does (on SixAxis)
--
e9b23e40 2764496125 S Co:002:00 s 21 09 0201 0000 0023 35 = 00ff01ff
7f000000 0003ff27 100032ff 27100032 ff271000 32ff2710 00320000
e9b23e40 2764507425 C Co:002:00 0 35 >
e99fe840 2766509714 S Co:002:00 s 21 09 0201 0000 0023 35 = 00ff00ff
00000000 0003ff27 100032ff 27100032 ff271000 32ff2710 00320000
e99fe840 2766521086 C Co:002:00 0 35 >
e9b23cc0 2768521311 S Co:002:00 s 21 09 0201 0000 0023 35 = 00ff01ff
4c000000 0003ff27 100032ff 27100032 ff271000 32ff2710 00320000
e9b23cc0 2768532755 C Co:002:00 0 35 >
e9b8e3c0 2770532954 S Co:002:00 s 21 09 0201 0000 0023 35 = 00ff00ff
00000000 0003ff27 100032ff 27100032 ff271000 32ff2710 00320000
e9b8e3c0 2770544425 C Co:002:00 0 35 >
e9b8f780 2770545424 C Ii:002:01 -2 0
--

Attached is a script from a while ago, when I was trying to figure out how
to get the Intec to rumble. Which runs without crashing machine.

Simon