After 5 years, the film on the glass balustrade on my balcony has started to bubble (see picture). The film itself comes off quite easily, but there is a sticky residue left behind. What product/solvent can I use to remove this residue ? There are 8 of these panels, so I've got a bit of work to do and would prefer a fairly inexpensive generic solution rather than a specialist product. Thanks in advance for any suggestions.
Sticky residue
Bubbling film