Welcome to the forum. smile

Yes; you can be sure that is the cause of the problem!

But meanwhile, I can't help wondering if it would also be "sweet and fitting" for the staff, having noticed the pitfalls mentioned, to revert to some earlier method of wiping over their kit.

Others have found that warm soapy water, applied with a soft cloth, does the job cheaply and efficiently; the only "downside" being the small effort required in obtaining the soap and warm water. smile

See also this earlier thread ... and this one.

If you don't inspect ... don't expect.