Behadrei brings a story from Rav Gershon Edelstein. Rav Edelstein fell ill during the holiday of SHvuos and had to be taken to the hospital Maayanei Hayeshua in Bnei Braq (Refuah Shleima!).

As Friday progressed and it became clear Rav Edelstein would be staying in the hospital through Shabbos, if not longer, he got concerned. He had made an eruv tavshilin on Thursday, erev chag, in his house, and now being stuck in the hospital nobody would be lighting candles in his home for Shabbos or cooking. Without any melacha to do on Friday in preparation for Shabbos, the Eruv Tavshilin bracha would be considered in retrospect to have been in vain. This greatly disturbed Rav Edelstein..

The problem was solved as the hospital administration had a pot of soup brought to Rav Edelstein's room and he stirred it, thus assisting in the cooking for Shabbos on Friday afternoon, turning the eruv tavshilin he had made on Thursday into an actualized bracha. All's well that ends well, as they say.

Now, what I do not understand is that I thought the purpose of the Eruv Tavshilin is to ALLOW one to do a melacha in preparation for Shabbos should it be necessary, and it almost always would be necessary for the lighting of the Shabbos candles at minimum. I do not recall learning that one MUST do a mleacha if having made an Eruv Tavshilin or else it would be a bracha levatala..

Was Rav Edelstein concerned due to a chumra of some sort or is it actually an obligation and if not fulfilled it would be a bracha levatala? Is this an interesting psak that a melacha must be done if one made an Eruv Tavshilin or is it a chumra?