70D Video issues with Tamron Lenses

I recently got my 70D and using with my two tramron lenses. 28-75 f/2.8 and 18-270 f/3.5-5.6. When I try taking video with these lenses, most times, The recording ends abruptly giving an error on the LCD monitor which says "make sure a lens is attached" or something similar. I have to go out of video mode and put it back in video mode to get it working again.

I have read similar issues with Tamron 17-50 f/2.8 on the internet where it was mentioned that this issue was fixed with a firmware upgrade from Tamron. I have contacted Tamron in the UK and they told me that there are no known issues with the lenses I have and they will need to repair them if I am having problems.

Any one else using these leses with 70D? I had no issues with these lenses on T1i (500D).

I have now realised that the issue is not just with Video. It is with Live view too.

Yes, this has been observed on a number of Tamron lenses. I encountered it too with my 17-50 f/2.8. Apparently you can send it back to Tamron for a firmware update to fix the issue. I didn't send it as I don't really use it on my 70D, and when I do use it on the 70D I use the viewfinder. But it is my favourite lens on the old 450D.

EDIT: Sorry... I see you already contacted Tamron. Well I recommend trying to talk to someone else at Tamron as I am positive this was acknowledged by Tamron when the 70D was released

I use a 28-75 2.8 and 70-200 2.8VC on my 70D liveview and video with no problem. I haven't shot long video (no more than a few minutes) so maybe I just didn't reach it. The 70-200 is pretty new obviously but the 28-75 is quite a few years old.

Thanks Dennis. I have talked to them too and got the same response. They are saying that the two lenses I have, don't have any firmware updates to fix this problem. I have faced the problem only once with Live view till now as I don't use life view often. But with videos, I had it cut out in under a minute few times, but I was able to shoot upto two mins some times.

I will do some more trials, this is not bothering me that much at the moment as I bought the 40mm stm pancake lens specifically for videos and primarily I would use these two tamron lenses to shoot through viewfinder. But It will be handy if they work well with Live View and Videos too.