I think it's not the image file, but the textual content of the messages itself. I catched one of the messages with the telegram-cli client, wrote it into a simple text file and sent it with cut&paste with telegram-cli to a tg account. When I then go with TELEports into the account from where I've
sent the text(!!!), it blocks also. The textual content is between the "cut here" lines:
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RT @TheCubanTech: @golrenier @FIDE_chess @mbejeranoj @Antonio_Sevila @dreg2k @WRV212 @aceraltos2001 @DeportesTeleSUR @InderCuba @Fedeajedrezsv @CirculodEspera @RadioCOCOnline @anavrin_rob @calamartinez86 @IPG1111 @diaz_capote @davidlahera15 @ReynierBatista @radiorebeldecu @jit_digital @TalanconNiurka @tele_rebelde @RadioRelojCuba @Daily_CVI @PortalCubaSi @lisychess @FedEcuAjedrez @CubaMES @CMontiller @CanalCaribeCuba @JuventudRebelde @Granma_Digital @USAChess @cvihdezlujan @caup_peru @DiegoLondo @chessbase_es @chesscom_es @GMJulioGranda @SabrinaVegaGut2 @chess24es @profesorajedrez @portalA21 @illescasmiguel @circulocapa @Fecodazajedrez Se está jugando #HOY #live la última ronda de @NorwayChess . Con 4 victorias seguidas @MagnusCarlsen llegó a 18 pts y está de líder. @AlirezaFirouzja , por su desempeño, es #1 ranking @FIDE_chess #top100 jr Partidas de la ronda anterior https://t.co/Zba6p9jxoW (via Twitter http://twitter.com/TheCubanTech/status/1438905423965392896)
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It takes TELEports some minutes to render this text into the screen. The problem is fully reproducible.
I will sent an example to the UBports_[ENGLISH] group. Just check this with the TELEports client.