Hey hurleh,
It's hard to tell with wireless, but it sounds like there's potentially interference which is causing those issues. I would recommend repositioning the router or moving equipment that may be causing an electrical interference to see if that improves the stability at all. I'd recommend trying some devices with ethernet cables rather than wireless to see if they experience the same problem - that way, we can establish if it's just a wireless issue or if there's maybe a problem with the line running slow in general.
Thank you, Bobby