Cannot export a chart to pdf - html2canvas is not defined

Hello,
I have trouble exporting graphs into pdf files. If I'm using a grid view the export works fine. When showing some type of a chart Export To Pdf functionality shows an exception: "Failed to export. An unexpected error occurred."
There are more details in browser's console:
flexmonster.full.js:9 Export Charts error: ReferenceError: html2canvas is not defined
at eval (flexmonster.full.js:9)
at Function.c4e.(anonymous function) [as load] (webpack:///./~/flexmonster/flexmonster.full.js?:9:1357909)
at Function.u0k.n8 (flexmonster.full.js:9)
at Function.u0k.Ad (flexmonster.full.js:9)
at R5B.mg (flexmonster.full.js:9)
at r1I.nca (flexmonster.full.js:9)
at n1f.eval (flexmonster.full.js:9)
at n1f.S7.dispatch (flexmonster.full.js:9)
at Function.H8k.mg (flexmonster.full.js:9)
at n1f.mg (flexmonster.full.js:9)
We have flexmonster running in a React app. Flexmonster's version is 2.6.0. Unfortunately I cannot reproduce this in JSFiddle.
Could you please tell me where to start?
Best regards,
Hannu