Ioannis Kasapakis

The problem is not so by the high  soil moisture but with the high atmosphere humidity and rains during flowering  and ripening period. So the plastic film I think will not help. If the above periods tgere are high atm humidity and frequently rains mayby you will had polination problems and priblems with insects and fungi in the ripe carob pods. The fruit set period and harvest period is about the same but with usual harvest practices there is not problem in the young fruits when you harvest the ripe. The ripe much easier drop down than young. Look the following video  

First read this book. https://www.bioversityinternational.org/uploads/tx_news/Carob_tree_Ceratonia_siliqua_L._347.pdf
For more information look and http://allaboutcarob.com/carob-uses/
I don't know about the climate in the zone that you ask but if during flowering period (Aug to Sept for North hemisphere) and fruit repening period July to Sept there are rains maybe you will have problems on fruit setting and with insects in the ripe carob pods. Recarding a previous comment if there are many flowers as usual in mediteranian countries there is not problem when you use vibration by woden stoles to drop down the pods because the percentange of flowers which drop down is very small.