The element button must not appear as a descendant of the a element

Hello,

Does anyone have any idea how to fix the following error:

Error: The element button must not appear as a descendant of the a element.
From line 112, column 3981; to line 112, column 4739
t=’_self’><button type=”button” id=”ubtn-1178″ class=”ubtn ult-adjust-bottom-margin ult-responsive ubtn-custom…-color:rgba(255,255,255,0.4);border-style:solid;background: rgba(255,255,255,0.01);color: #ffffff;”><span

My website is: https://www.tgfsecurity.co.uk

Thanks in advance
James