Low grade LPG fuel contains excessive tars (honey as you say) and mess-up things. Many of the Japanese lift trucks had a device up thru the 1990's called a tar trap. The purpose was to collect the tar in the line between the tank & primary regulator. This trap had a drain plug on the bottom so the tar residue could be periodically drained.
You may want to talk to various LPG suppliers in you area about this issue to see who has the "good stuff" & who don't. Another suggestion is do a Google search on how you can determine what is good or not.