Why some of PNGs cannot display normally when changing its src in lv_timer

Error description

I created two images ,and try changing their source in timer callback.It results in one update normally while another not. the abnormal one was display to a vertical black bar.

I tried change the abnormal one's source to another, and then the problem come up as well.

Finall I find thing is that some PNG images' src can only be changed in timer once,  but with no limit without timer. And only some of PNGs behave like this.

Is there any limit on PNGs to make it work normally or some suggestion on using of lv_timer?

With great glad to recv any guide from you!