Canon 70-300 lens IS not working with C300MKIII

[boosh]

Not sure if anyone has come across this before. I'm ready to send my 70 - 300 Canon lens off to get a new IS unit fitted but I've realised it works perfectly fine with my Canon R5 (Canon R5 internal IS turned off). With my Canon C300MKIII the IS works for about 10 seconds and then disengages and stops working. Anyone have any experience of this happening? The internal IS on the C300 is ok but the IS on the lens is much better and doesn't result in any cropping so I would like to get this working properly. It's a mystery that it works perfectly fine with my Canon R5 but not the C300MKIII. Any advice on this very much welcome.

 

[indiawilds]

Often older lenses have firmware issues and don't focus with certain new cameras. You have to get the lens checked. The firmware in the Cinema EOS cameras and the R5 is different, so you get different response.