"The 'timeframe' argument is incompatible with functions that have side effects" – what does it mean?

I moved my rich VWAP indicator out to a Pane to avoid making too big mess on the chart but here in the Pane, I obviously don't see the price (close) there. So I decided to draw it using a box().

var box PriceRectangular = na
if(na(PriceRectangular))
	PriceRectangular := box.new(left=bar_index, top=close, right=bar_index, bottom=close, border_color=#8888880a, border_width=2, bgcolor=#00000000, extend=extend.right)
	box.set_left(PriceRectangular, bar_index)
	box.set_border_width(PriceRectangular, 2)
	box.set_top(PriceRectangular, close)
	box.set_right(PriceRectangular, bar_index)
	box.set_bottom(PriceRectangular, close)
	box.set_border_color(PriceRectangular, #8888880a)
	box.set_bgcolor(PriceRectangular, #00000000)
	box.set_extend(PriceRectangular, extend.right)
else
	box.set_left(PriceRectangular, bar_index)
	box.set_border_width(PriceRectangular, 2)
	box.set_top(PriceRectangular, close)
	box.set_right(PriceRectangular, bar_index)
	box.set_bottom(PriceRectangular, close)
	box.set_border_color(PriceRectangular, #8888880a)
	box.set_bgcolor(PriceRectangular, #00000000)
	box.set_extend(PriceRectangular, extend.right)

The code itself works elsewhere (on-chart) but here, it fails with the error message above. Is there any workaround?

You will mostly have this issue if you are using any drawing objects. It means that, Tradingview is unable to do a multitimeframe anlaysis of your code automatically.

To get rid of this error, you need to remove the statements timeframe="", timeframe_gaps=true from your indicator() call.

If you really need multi timeframe analysis, you should do that yourself by using security() function.