Ricoh warns against using non-original accessories on the GR III cameras (Google translated):
Precautions for using non-original accessories of GRIII series
Dear Customer: Hello:
In order to improve your GRIII series camera experience, Ricoh Imaging Instrument Service Center kindly reminds you that when choosing non-original accessories, please pay attention to the following:
Please try not to use UV mirror
Because some UV mirrors are too heavy, the lens nameplate cannot bear the weight of the UV mirror, which will cause the lens nameplate to fall off. The use of adhesive UV mirrors will cause the detachable nameplate to fall off and leave marks that cannot be erased, and sometimes even the lens cover will be glued together. Inferior UV mirrors will also affect the imaging quality.
Do not use inferior non-original batteries
Inferior non-original batteries will cause the contacts of the battery compartment to sink and cause poor contact, making it impossible to use the original batteries. Sometimes it can also cause the motherboard to fail to work properly.
Do not use non-original lens rings that do not meet the specifications
Some commercially available non-original lens rings do not meet the requirements of the GRIII series. Forcible installation will affect the contact points, causing the camera’s focal length to switch back and forth between 35mm and 50mm.
Do not use inferior fast charging power bank
When charging the camera, if you use a low-quality fast charging power bank, it is easy to burn the main board of the camera or the camera cannot be started normally.
If the camera fails due to the use of non-original accessories, the relevant maintenance costs incurred after verification will be borne by the user, and will not be covered by the warranty. (source: Ricoh China)